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January 13, 2002

In the Pit, Dark Relics and Last Obstacles

By ERIC LIPTON and JAMES GLANZ

PATH train car, peeking out from a window deep in the rubble. A sign directing commuters to 4 World Trade Center, a building that has now vanished. A series of basement floors, the walls torn away, leaving the structure exposed to the winter winds like pueblo dwellings. A Mrs. Fields bakery poster, offering "Big Fun" cookies to customers who no longer come. These are the last relics of what was once one of the most recognizable landmarks in the world, a place that is now an unfamiliar, disorienting moonscape. But these markers, some hidden in dank, dark underground caverns and passageways, others exposed in a giant, terraced pit, still have a purpose. They point to a final set of engineering challenges at the World Trade Center site, tasks unlike anything the construction crews have faced in four months of day and night work.

No longer are they grabbing at loose piles of debris, or using demolition balls to knock down shells of crumbled and burned-out office towers. Not even the smallest shard of a building remains above street level on this 16-acre site where two of the world's tallest structures once stood.  Now, the army of laborers — along with teams of firefighters still diligently looking for human remains — have moved below ground, sinking floor by floor into the subterranean realm of an office complex that, even in the horrific implosion of the towers, somehow was not smashed flat.

Like archaeologists digging among ancient ruins, they must exhaustingly think out each step. The unlighted, below-ground floors and the scattered structures in whose shadow the crews labor are not just the last vestiges of an office complex. They are also buttressing an adjacent wall — known colloquially as the bathtub, or slurry wall — that surrounds much of the site and keeps back the waters of the Hudson River.

So even as they cart out debris and disassemble sections of these underground floors, the crews  must sink thick steel cable bundles, called tiebacks, into the bedrock below the bathtub wall to brace it. In essence, they are sawing down a tree while suspended in its branches — except that this is all underground.

And that is just the start of it. Once-buried tunnels that daily carried tens of thousands of commuters to this site are emerging into the winter light. The final PATH train at World Trade Center — a train that never left — has been exhumed and is visible, listing to its side, the sun shining through its windows, waiting to be lifted from its resting place.

Inside the deep, wide-open pit that has been dug — so deep in spots that the bedrock is all that is left — a pond of greenish water has collected, some of it from rain, some from small leaks in the bathtub walls, some from water percolating up from fissures in the bedrock.

Only an effort that has been little short of epic has brought the teams to this underground phase of the cleanup. To date, according to the city's count, 1,036,837 tons of charred steel, smashed concrete, crumpled ductwork and other assorted debris has been removed from the site since Sept. 11. Engineers originally estimated it would be a 1.2 million-ton cleanup job; now, the city says, with a likely wrapup date of June, the total could rise to 1.5 million tons. But those bare numbers do little to describe the radically changing topography.

To the north, a ring of partially intact basement floors rises up like battered cliffs, encircling the last visible mass of tangled steel from the collapsed north tower. The mass of debris, which workers here call "the crater," is a raw exhibit, and the final one at the site, of the incomprehensible violence that brought down the towers. To the east is the former shopping concourse, where the last traces of places like Natisse International hair salon, a newsstand and the Kelly Express photo store are being ripped out to make way for trucks and other heavy equipment. At least for now, bottles of nail polish and shampoo are still strewn on the floor at the hair salon, and lottery stubs and Sept. 11 newspapers litter a hallway outside the newsstand.

To the southwest is the deepest part of the dig, a spot where virtually all the remains of the 110-story south tower have been lifted up and carried out. Looming above that pit is about 45 feet of slurry wall, which has an ancient look, like an excavated section of a medieval castle. The exquisitely careful step-by- step ordering of tasks in each section of the site is clear to everyone. "The mantra is, `Remains recovery, excavation and tiebacks,' " said Kenneth Holden, commissioner of the city's Department of Design and Construction, which is leading the cleanup. The choreography involves search teams, workers with cutting torches, heavy demolition equipment and towering drilling machines for the tiebacks.

The biggest remaining chores are concentrated in the northwestern section of the site. It is here that clifflike faces have formed, in a Niagara Falls-shaped semicircle, from what is left of multifloored subbasements that now end at a ledge to nowhere.
That semicircular shape was carved by a deadly barrage of steel members that cascaded from the north tower, as well as detritus from smaller structures, smashing a hole through an adjacent eight-story building all the way down to the bedrock. So much fell into this spot that the pile of compacted debris now fills the crater.

Nothing is simple at this site. Workers cannot merely clear out the crater, as the pressure of the debris helps support the nearby slurry wall. So as the debris is removed, holes must be drilled through the slurry wall along Vesey Street, angling downward toward the bedrock. There the tieback cables can be anchored like guylines around a tent.  Yet even this task is complicated. Elsewhere at the site, a huge drilling apparatus can easily be lowered through the air on cranes or positioned using heavy crawlers. But partially intact floors project from the Vesey Street wall, denying the crews and their equipment direct access. Even if machinery can squeeze in there, the weakened basement floors will hold only so much. "I don't want to put a 30,000-pound weight on the slab and have the machine  fall through," said Paul Ashlin, a senior vice president at Bovis Lend Lease, which is now managing the cleanup work for the city.

Planners are debating whether to use smaller, mobile machines that could clamber through the darkness of the intact floors. "The intent would be to possibly get a small drilling rig in, that could operate in a small height," said Pat Muldoon, senior vice president of Amec Construction, which is working at the site. The small drilling rig he was referring to weighs about 10,000 pounds. No matter how intense the planning, or how skilled the engineers and laborers assigned the task, unexpected disruptions still stall the work. This happens everywhere, even in spots that are supposedly easier to handle.

Last week, as a crew from Berkel & Company Contractors installed a tieback near where the Marriott World Trade Center once stood, they hit a buried piece of steel, 50 feet down into the soil and 29 feet into the bedrock, just one foot short of their goal. They spent hours trying to get around the steel, trying to push that one final foot. But instead, they broke off the business end of the drill, called the hammer. "When do you cut your losses?" said Ken Blum, a supervisor at Berkel & Company, a Kansas company that is helping install tiebacks. `If you start to damage more equipment than the $5,000 hammer is worth, I guess that is when you leave it buried and it becomes part of the foundation forever and you move on."

The work in the pit is just as trying.  So compressed are  backhoes and grapplers reach for pieces of twisted steel, they must struggle again and again to yank them free. The rear end of these massive vehicles are lifted precariously into the air as they pull at the buried debris, and they rock back and forth like children's toys. With enough tugs, they wrestle even the stubborn pieces free. And with each chunk pulled out, the pile shrinks down toward the bedrock. Dump truck after dump truck is filled and sent up the muddy ramp to the city. The cycle never stops; trucks carrying fuel and replacement tires come right down  into the pit to keep the backhoes running. The only pause is when a firefighter sees a helmet, a coat, a boot or even a suit — any sign of human remains. Then it is the garden tools and hand-held picks that take over for a search that lasts as long as it takes. Demolition work does not restart until after a stretcher draped with an American flag is carried out, between two lines of firefighters, standing silent and tall.

 With a hole now almost 70 feet deep in some places, there is a not- so-surprising result: accumulating water. A series of wells has already been drilled around the outside edge of the site, into which drainage pipes have been dropped to siphon off groundwater, relieving pressure on the slurry wall.

Inside the hole, engineers have installed pumps to drain the pond, which has turned green from the fuel oil and other contaminants squeezed from vehicles crushed in the basement by the collapse.  Even as the work to clear the disaster site progresses, those anxious to start rebuilding are making their first moves. The lower reaches of West Broadway, just north of ground zero, are being ripped open so that debris that fell into the 1 and 9 subway tunnel can be extracted.

And last Thursday, a bit farther south, a team of New York City Transit engineers and contractors went underground, past the abandoned turnstiles and token booths of the Cortlandt Street station that served the trade center. It was a journey, one engineer said, that felt like a visit to the Titanic. Wearing respirators and hard hats, equipped with flashlights and gas meters to detect any chemicals lingering in the air, the team lumbered along the station's platform toward a truly hellish sight. A chunk of the south tower had tumbled down, dozens of stories, to a final stop right there in the gloom of the tunnel.

The engineers gaped at the destruction. They heard only the trickling of water and the sound of others approaching, boots swishing through the layers of slushy ash and crumbled concrete along the floor. Otherwise, there was silence as the contractors and engineers surveyed the work ahead. The subway tunnel floor, ceiling and walls must be rebuilt, new track installed, the signal and communications system replaced, all somehow by November or December, when the line is set to
reopen. "It gets overwhelming," said Joe Siano, a transit agency vice president who is overseeing the rebuilding effort. "Then you realize how many hours there are in the day. It is not just 8, it is 24. And you realize how much will and energy and spirit there will be on the part of the contractors to get the job done."

http://www.nytimes.com/2002/01/13/nyregion/13SITE.html?todaysheadlines