

The Biggest Foundation by Edith Iglauer Issue of 1972-11-04

Posted 2001-09-13

This piece, written in 1972, looks at the construction of the World Trade Center's twin towers, at a time when they were a symbol of possibility.

Soaring above the lower end of Manhattan Island is the world's largest cluster of tall buildings, whose oblongs, spires, and turrets have, since this century began, given New York the most spectacular skyline anywhere. Each one of the towers whose upper extremities pierce the clouds is rooted, below the city's surface, in a huge, unseen structure that may itself be the size of a ten-story building. The finishing touches are now being put on the biggest foundation in the world, which is below what are, as of now, the highest pair of buildings in the world. These are the twin hundred-and-ten-story towers of the World Trade Center, built for the Port Authority of New York and New Jersey. Nine or ten good-sized office or apartment buildings could have been fitted into the hole that was dug for the Trade Center, and the foundation proper is six times as large as that of the usual fifty-story skyscraper and four times as large as its closest competitor—the basement of the neighboring sixty-story Chase Manhattan Bank Building.

On a hot, dry summer day nearly seven years ago, I went down to the corner of West and Cortlandt Streets to witness the initial tests of some basic equipment for the construction of the main foundation walls of what would be the biggest building job ever attempted—in height of the structures, size of the foundation and excavation, and almost everything else. I was there to witness the test with Robert E. White, who is executive vice-president of Spencer, White & Prentis, a firm of foundation experts that is almost always called in whenever architects and builders think anything complicated or unexpected may occur below ground. Robert White and his brother Edward, president of that firm, are old friends of mine, and when I had mentioned not long before that I had always wondered what kept the tall buildings in New York anchored to the ground or whatever was underneath it, they suggested that I observe some of the steps in the construction of the foundations for the Trade Center. I knew that besides the two skyscrapers, each thirteen hundred and fifty feet high, at least three other buildings would be erected on the sixteen-acre site: an eight-story structure for the United States Customs Bureau and two nine-story ones for exhibits, meetings, and trade activities, around a five-acre plaza. To accommodate this extraordinary new assemblage within fourteen blocks of jammed lower Manhattan, the Port Authority had condemned a hundred and sixty-four buildings then standing on the site—including the big, rambling headquarters of the old Hudson and Manhattan Railroad, now the Port Authority Trans-Hudson System, known as PATH—and had closed off parts of five streets that ran through it. I had studied the map, and knew their names—Cortlandt, Dey, Fulton, Washington, and Greenwich. I also knew the names of the four streets bordering the site: West Street, running parallel to the dock area and beneath the West Side Highway along the bank of the Hudson River; Liberty Street, to the south, which is only a brief walk from the Battery; Church Street, a step from Trinity Church, on the east; and, to the north, Vesey Street, where the New York Telephone Company has its headquarters. The city had made a neat bargain with the Port Authority. In return for municipal assistance in obtaining the huge site, the Port Authority was going to add about twenty-four acres of new real estate to New York City by dumping the dirt and rock that would be excavated—more than a million cubic yards, or enough to make a pile about a mile high and seventy-five feet square—inside a great riverside cofferdam, or bulkhead. On this man-made peninsula, with a base extending from the old Pier 7 to the old Pier 11 and the Central Railroad of New Jersey ferry slip along the Hudson, plans called for streets, parking facilities, sewers, mains for water, electricity, and steam, and, eventually, apartment houses, stores, and various other buildings—parts of a complex to be known as Battery Park City.

The backbone of Manhattan is a rock ledge, which actually can be seen in Central Park and a number of other places. Starting at Fourteenth Street, it goes gradually beneath sea level, and extends under Governor's Island, Staten Island, New Jersey, and possibly as far as Pennsylvania, where similar rock—known here as Manhattan Schist—has been found. At the World Trade Center site, the rock is seventy feet below sea level, and above it is a nightmare for all construction engineers—filled land. Two hundred years ago, New York City was a little colonial town at the tip of the island, with docks and piers reaching like fingers into the rivers on either side. As the city grew, the dirt and rock dug out for cellars and, later, for subways and other underground installations, was dumped into the rivers to create new real estate, and it is estimated that the island's shoreline was pushed out about seven hundred feet in the area around the Trade Center. When a heavy building rests on bedrock, its engineers can sleep peacefully. Once they have dug to such rock, that's as far as they have to go, which made Manhattan a superb location for many of the first skyscrapers. The bedrock is so close to the surface in midtown—only eight feet down at Rockefeller Center—that sometimes it has to be blasted out for basements.

As Robert White and I were walking toward the test site, he said, "Some foundations, like those of the Empire State Building, are so routine they aren't interesting. A one-story service station built on a swamp could be more exciting. But on this kind of filled land there is nothing but trouble," he said, looking pleased. "For a typical downtown New York skyscraper, you normally dig down thirty or forty feet, but this foundation will have to go anywhere from sixty to a hundred feet. Around here, there's usually ten or fifteen feet of fill near the surface—rubble, old bricks, old anything. Then you have five to twenty-five feet of Hudson River silt—black, oozy mud, often covering old docks and ships. Down here we may hit parts of an old Dutch vessel called the Tijger, which burned off Manhattan in 1614. Below the silt, there's maybe a dozen feet of red sand called bull's liver, which is really quicksand—the bugbear of all excavating. The more you dig in it the more everything oozes into the hole. We expect to find it here, but we know how to deal with it. Under that is hardpan—clay that was squeezed dry by the glacier and its accompanying boulders. Finally, beneath the hardpan, there's Manhattan Schist."

As we entered the lot where the test was to take place, I noticed water running from a small pump into the gutter. White said, "People passing by complained that we were wasting water, so a city inspector came around. He laughed when he found that we were pumping out tidewater. We're working below the level of the Hudson, with the same tides as the Battery—varying from two to six feet." The lot was bare except for an enormous green crane on red wheels, a pile of bags marked "Bentonite," several oxygen tanks, a large gray hydraulic jack, and a blue box, which White said was for cutting wires. A dozen men, some in business suits and some in grimy work clothes, all wearing hardhats, stood next to a strip of concrete about twenty-five feet long and the width of a small sidewalk. White explained that the concrete strip was the top of a sample piece of foundation wall, extending about ten feet below the ground, and that what I was going to see demonstrated was part of an unusual system of foundation construction that would be used on this job. Projecting from the concrete slab, at a forty-five-degree angle, were three pipe casings, inside which, he explained, groups of rods, wires, or cables, all known as tiebacks, extended, unseen, a hundred and thirty feet down, where they were anchored to bedrock. Concrete for the permanent walls making up the foundation's perimeter, thirty-one hundred feet long and about seventy feet deep, would be poured into trenches dug to the walls' width and depth before any other excavation began. Then workmen would dig down to install tiebacks, such as those here, and they would be stretched to a tension greater than the underground pressure behind the walls, to hold them up while all the earth, rock, and other matter they enclosed was removed. Ultimately, a complex system of interior concrete partitions and floors, extending six stories below the level of the street, would take over the job of supporting the outside foundation walls. Then the fifteen hundred tiebacks would be de-stressed and cut off. The purpose of today's tests, said White, was to determine which of the three different sorts of rods, wires, and cables inside the pipe casings would make the most effective tiebacks.

The group gazing at the section of wall opened ranks for us. Several of the men proved to be Port Authority officials: John M. Kyle, the Chief Engineer, who was a short man in a white helmet inscribed "Lincoln Tunnel, Third Tube, Last Bolt, June 28, 1956;" Arne Lier, the structural-design expert; Martin S. Kapp, head of the soils division, a big friendly engineer in overalls; Harry Druding, the engineer in charge at the site; and Leon Katz, the Port Authority's information officer. (Both Kyle and Kapp, who succeeded him two years ago as Chief Engineer, died of heart attacks before they could see the Trade Center completed.) The rest of the men were from West Street Associates—a group of five heavy-construction companies (of which the Whites' outfit was one) that had banded together with Slattery Associates, Inc., the lead contractor, to take on most of the technically tricky, financially risky twenty-seven-million-dollar job of underpinning the World Trade Center.

Protruding from one pipe casing were more than a dozen cables, now slack, whose far ends were cemented underground. Each of these was now to be pulled taut separately by the hydraulic jack exerting as much as twenty tons of tension to test the tieback's strength. This machine was moved into a position where its wedge-shaped jaws could grip one of the cables, and it began drawing the cable up tight. As we watched, the pressure gauge on the jack moved to two thousand pounds per square inch—which represented a quarter of the cable's theoretical breaking point—and White explained that the steel cable would be stretched about eight inches, like a rubber band. The needle crept to three thousand pounds, then four thousand. When it was at five thousand, someone said, "Get back in case the wire snaps." Everybody moved back a few feet, and White said, "I saw two steel rods break during this sort of test in West Virginia, and they shot like spears halfway across the Monongahela River." Everyone moved back a step farther. Then Kyle called out, "Sixty-seven hundred pounds per square inch! That should be enough. That's twenty tons on the cable." It was announced that the wall was taking the load well, having moved a mere seven-eighths of an inch. If it had moved substantially, that would have meant that the tieback had pulled away from its anchorage. The jack went to work on a second cable, then a third, and within an hour or so it had been ascertained that all the different tiebacks stood up well under the strain. The contractors therefore decided on the one that they believed would be the most economical—a seven-wire cable about a half inch in diameter.

After the test, I accepted Kyle's invitation to accompany him to his office at the Port Authority headquarters, at Eighth Avenue and Fifteenth Street, for further enlightenment. I remember his saying, as he showed me in, "Maybe the Walls of Jericho fell down because they weren't built on good foundations." In his outer reception room, he halted before an old topographical map of Manhattan Island—published by Egbert L. Viele in 1865 for the use of sewer engineers—which showed the island's natural springs, streams, and marshes before they were covered over by building projects. Kyle told me that this map has been a basic reference source for all underground planning and construction in New York for years. Kyle said, "Engineers make large-scale map blowups from it of the areas where they're working. Every existing stream in Manhattan shows up on the Viele map. There's the one at Forty-first Street that we hit when we were building the Port Authority Bus Terminal, and there's Minetta Creek, in Washington Square, which comes out in a hotel lobby as a fountain. And there you can see that we have a spring right under this building, whose water we use as a coolant in our air-conditioning system to save city water, and to wash down the Holland Tunnel during droughts."

Kyle told me that the World Trade Center foundation job was the most difficult and most interesting he had ever faced, and went on to explain why. Conventional deep foundations for tall buildings in New York, he said, are built by excavating the site, driving steel sheeting down to bedrock, propping it with heavy braces inside the cut, building wooden wall forms next to the sheeting and pouring concrete into them, removing the forms, installing basement floors, and, finally, removing the wall braces and the sheeting. If the ground contains excessive moisture, a mammoth, heavily reinforced slab of concrete, sometimes as thick as fifteen feet, is poured as a bottom floor, to counteract any upward pressure from the underground water. None of these orderly procedures could be applied with reasonable economy to the Trade Center site, he said. The original shoreline of Manhattan runs close to Greenwich Street, which bisects the site north and south, and this is a dividing line between good and bad foundation-building land. The area that had concerned the engineers from the outset was the western half, beyond the original shoreline, where borings eighty feet apart indicated that what was below was Hudson River silt loaded with underground obstructions—wharves built with wooden cribbings, foundations of stone and brick, crisscross timbers or piles, boulders, riprap, rocks that had been used as ballast in sailing ships coming empty from Europe to take on cargo, and even some of the ships themselves. Both of the Trade Center's skyscrapers, the Customs Building, and half of the plaza would occupy this part of the site, Kyle said, and their total weight would come to a million and a quarter tons, or twelve times as much as the weight of the George Washington Bridge, including its concrete decks, its steel anchorages, and everything but vehicles.

In a foundation of orthodox design, skyscraper towers, with special concrete-and-steel footings in the rock, would have sufficient weight to stay put in ground as watery as the tidal fill around the Trade Center, but the surrounding streets might fall in and the smaller buildings might settle down, or, worse, pop up. Insufficiently anchored tunnels have risen from river bottoms to haunt engineers who miscalculated the force of underwater buoyancy, and buried gas tanks are notoriously jumpy. However, it is doubtful whether conventional foundations could have been built at the Trade Center without the contractors' going broke from cave-ins and other difficulties, such as the slow pace of excavating the entire site before starting construction, the need to pump tidal water out the whole time, the tortuous process of driving piles or steel sheeting down to bedrock through the accumulated debris, and the obstacle for other construction imposed by the huge braces needed to keep the peripheral walls from falling in until the inside floors were in place.

In addition, Kyle said, the World Trade Center had a problem that, as far as he knew, no foundation engineer had ever before faced: a railroad had to be kept running inside the foundation area while digging went on around and beneath its tracks. Actually, two railroads go through the site—the I.R.T. local subway line to South Ferry and the PATH System, a fourteen-mile line running between Newark, Hoboken, Jersey City, and Manhattan through tunnels under the Hudson River. PATH crossed the site in two five-hundred-foot cast-iron tubes, almost three-quarters of a century old, resting on beds of mud. Some way had to be found to jack up the tubes, through which about a thousand trains rumbled back and forth daily, carrying more than eighty thousand passengers, without disturbing either the trains or the passengers. Ultimately, the tracks would be relocated under the Trade Center and the old tunnels removed.

The solution to all this was a daring one: to build one huge basement, sixty-five feet deep in some places, a hundred feet deep in others, that would take the form of a watertight box (but what a box!) occupying eight acres on the treacherous eight-block western half of the site. What the engineers were really doing was building a four-sided dam around the troublesome part of the site. The bottom of the box would be bedrock, into which the walls would be tightly socketed to keep water out. During the construction of the walls, water trapped inside could be removed as the filled land was dug away and the bedrock emerged. Then the work of digging beneath PATH and constructing the basement area—containing a new PATH terminal, the underground home of the Trade Center's maintenance and air-conditioning equipment, an emergency electric generating plant, garages, and truck docks—could proceed with maximum efficiency. As it took shape, this box, the largest single basement that Kyle or any of the West Street Associates knew of, came to be called the Big Bathtub, and, finally, just the Bathtub.

While planning the Trade Center foundation, Kyle told me, he inspected subways and other underground work in Paris, Brussels, London, and, finally, Milan, where a new subway was completed in the late nineteen-sixties. In all these places, a Milanese firm named ICOS, which specializes in building walls in wet areas to keep water from flooding construction sites, had used a new process called the slurry-trench method. In Montreal, Toronto, and at a dam in Pennsylvania, an affiliate of the Italian company, the Icanda Corporation, Ltd., of Canada, was doing the same kind of work, and Icanda was eventually hired to work jointly with the West Street Associates and actually construct the Bathtub wall. To a layman, the idea of building a multimillion-dollar foundation wall anywhere from sixty-five to a hundred feet deep underground, blindly, without excavating on either side of it, is bound to seem the height of folly, and I told Kyle so that afternoon. He laughed, and said he would try to explain why it was the most practical solution. The key to the slurry-trench method is the use of a volcanic ash, or clay, called bentonite—after Fort Benton, in Wyoming, where deposits of it first were found, in the eighteen-forties. The peculiar property of bentonite, a powdery clay, is its ability to absorb enormous quantities of water in an excavation, after which it is strong enough to hold back the surrounding earth. The petroleum industry began using bentonite instead of metal casings in oil-drilling holes around 1900. When mixed with water, bentonite creates a counter-pressure to the push of surrounding earth and water, and prevents cave-ins—just how is not understood, though some experts believe that an undetectable electric charge may be involved. "If you dig a trench and put down bentonite in the right mixture, it will hold up the banks," Kyle said. "The bentonite that is attached to the earth will stay attached even when concrete goes down and displaces the water in it. The stuff acts like a membrane, and the part that sticks to the wall holds the wall up. It annoys hell out of you when you can't figure out why that is, but, basically, we aren't interested in the theory. The important thing is that it works." The Bathtub wall, he said, was to be constructed in sections. Trench segments twenty-two feet long, three feet wide, and seventy feet deep would be dug and filled with slurry—a mixture of six per cent bentonite and ninety-four per cent water. As dirt was removed it would continuously be replaced by slurry, so that the trench would always remain full and the sides would not fall in. The digging would continue down into bedrock, with about two feet of the rock itself chipped away to give the wall a proper footing. Then a great cage of steel rods—shaped to fit into the full length of each twenty-two-foot segment of trench and holding a number of forty-five-degree-angle steel guides for the installation of tiebacks—would be dropped into the soupy mix to reinforce the concrete. Next, the concrete itself would be poured into each section. As the liquid concrete rose to the top of the trench, it would displace the slurry, which would be pumped into the next section of trench. As each section of concrete wall was completed, the workmen would excavate on the inner side of it to install tiebacks reaching diagonally down through the soil behind it. Then the earth inside that section of the Bathtub could be removed. With ten or fifteen machines moving simultaneously along the perimeter, Kyle figured, the outside foundation would take about a year to complete.

Before I left him that day, Kyle remarked that, of course, all kinds of sewer, water, and steam pipes and electric and telephone lines running through the site would have to be rearranged, adding that such work is normal in new construction, but this would be the biggest relocation job in the history of the New York Telephone Company. The company's main office was right next door to the Trade Center, at the corner of West and Vesey Streets, he reminded me, and the principal trunk lines for all phone communication between major cities in the United States and to the world outside—including the hot line to Moscow—were under what had been Greenwich Street, in the very middle of the site. Local telephone lines customarily run under public thoroughfares, too, and these would all have to be moved to the West Street boundary. As for the long-distance lines, two huge manholes, or vaults, opening into the two tunnels of PATH were to be constructed, to reconnect these lines inside the tunnels for their route across the Hudson. The vaults underneath West Street would also serve to pin the cast-iron PATH tubes to bedrock.

In order to connect the new telephone wires, one by one, to sections of cables that would be brought into the new manholes and thence dropped into the tunnels, splicers would work in shifts, sitting on benches inside the vaults and splicing each cable progressively without interfering with telephone service. Such splicing "alive" could be done so skillfully that conversations would continue, with the customers unaware of what was happening.

It took more than a year to clear the Bathtub site of condemned buildings. This had been an area of small shops, many engaged in selling hi-fi equipment, and many of the store owners left reluctantly. There were also two residential tenants in no hurry at all to depart—one of them a penthouse dweller who loved the river view from his eighty-five-dollar-a-month apartment atop a five-story office building, the other a monkey that escaped from a pet shop when it was about to be torn down, built a nest in a pile of beams, stole enough bananas daily from a nearby fruit stand to stay alive, and eluded workmen for months. In any such huge project, the pattern of logistics demands immensely precise timing and coördination. Before the demolition of the old structures was half completed, therefore, construction of the Bathtub wall had begun, excavation inside the sections of wall that were in place was under way, and the cofferdam at the river's edge was receiving excavated fill. Wherever twenty-two feet of perimeter land had been cleared, Icanda's workmen jumped ahead and built another section of wall, so that practically the entire wall could be completed before the last of the condemned structures inside the Bathtub was demolished. The steel framework for the two skyscrapers, anchored in bedrock, began to rise aboveground while workmen underground were still digging out boulders from corners and dirt from underneath the PATH tubes.

Construction engineers groan at the prospect of finding relics when they are excavating an area with a complex history, for fear their work might be delayed while archeologists poke through the rubble, but nothing worth that effort ever turned up. The sunken ship Tijger never appeared—at least, not in any recognizable form—perhaps because powerful shovels smashed through underground obstructions as the excavations for the wall were completed. Timber cribbings were particularly wicked to break up, because lumber underwater can be just as hard after two hundred years as the day it was sunk, though it may disintegrate a week after it hits the air. A cannister from the cornerstone of the old Washington Market turned up, full of newspapers and the cards of the produce people who had taken stalls there. A century-old bedroom slipper came to light, as did an eighteenth-century forged nail, several clay pipes, a large Portuguese fishing gaff, and a variety of antique tools and ship fittings, including rudders and several anchors of a pattern not made after 1750. An enormous iron anchor, weighing about a thousand pounds, required nineteen men to carry it up out of the site, and it now rests against a concrete wall in the Trade Center's heating-and-refrigeration plant, in the sixth-level basement—the very bottom of the Bathtub. Ancient cannonballs and bombs, the muzzle of a cannon, old bottles, bits and pieces of old china, and one small gold-rimmed cup with two hand-painted lovebirds on it turned up in the digging. Of all the china objects found, it alone was intact. A lot of coins were rumored to have been dug up, but they did not materialize in the front office.

From time to time, I dropped by the site to watch the activity in the cut far below—ants in perpetual motion to the throbbing of a chorus of heavy machines. Seventy feet above, the ground where I stood vibrated. One summer day a couple of years after my initial visit, Kyle suggested that he take me on a formal tour, since the operation had reached a point where demolition, excavation, and construction were going on simultaneously, and the Telephone Company was about to finish its splicing in the ducts inside the recently completed manholes. I stepped out of a cab on West Street in the middle of the afternoon and stopped for a moment, facing the river, struck by the beauty of what was left of an old ferry slip that was being demolished between the Trade Center and the new landfill in the river. Only the façade was intact, with high Victorian windows and a handless clockface. At the sides, the steel and wood of the old walls were falling away, dripping down like lace, and the sun was reflected hotly in a second-floor window that still had glass in it. This dreamy remnant looked ready for instant collapse. Beyond, I could just see the tops of the large cylindrical caissons that made up the cofferdam bounding the huge twenty-four-acre rectangle of new Manhattan real estate in the river. The center of the rectangle was a trifle wet, but the cofferdam was well filled with excavated material from the Trade Center foundation. I turned back toward the site, and saw that the surface area of the Bathtub was now almost cleared; there remained only part of a steel building frame with an elevator shaft still clinging to it, and a large stone edifice, the Marine Midland Bank Building, which appeared to have been built to last forever—except that it was not going to; looking up, I saw the iron ball of a demolition crane pounding away at the already roofless top story. I subsequently learned that it took four months to demolish this stubborn old fortress.

Kyle was waiting for me at the corner of West and Vesey, and we walked around the outside of the Bathtub, now clearly demarcated by the sections of wall already in place. Kyle paused to show me a particularly noteworthy machine, an enormously tall blue rig on a blue A-frame that was travelling on rails along the surface, digging the trench for a section of wall. All Icanda's machines were painted blue; this one, called an Adiges, and four or five other like it, had been imported from Italy for the job. A three-ton clamshell bucket hung from the peak of the A-frame and was equipped with jagged teeth to chew away the ground. Icanda, whose contract called for cutting not only through the ground but several feet into bedrock, had discovered that boulders and ancient timber obstructions were more formidable than had been anticipated, so it had then brought in two other pieces of special equipment—a rotary drill from the oil wells of Texas, so big that it had to be disassembled and transported to the site on three trucks, and a rock slicer, which had been air-expressed from ICOS's Milan shop. This monster, which had a giant blade attached to a lofty rectangular rig, could shave off rock wedges an inch thick, like a cheese slicer, but it met its match in Manhattan Schist, which is intermixed with hard, abrasive quartzite, and quickly dulled the slicer's blade. In fact, neither machine proved useful, and Icanda eventually resorted to old-fashioned methods of drilling, crushing, and hammering rock.

Against the backdrop of exposed brown soil and gray rock, blue, yellow, and orange machines down in the excavation were spots of bright color, and moving trucks of other vivid hues made additional flecks of brightness—especially the red trucks that carried explosives. Varicolored workmen's helmets also dotted the landscape—blue for Icanda, yellow for the Port Authority, green for Slattery, white for PATH, and an occasional silver or other odd-colored hardhat that was a treasured good-luck possession of its owner. Up on the surface, the Adiges machine near me stood next to a mixer pouring wet bentonite into the open trench, whose surface was a runny beige soup. Some distance away, concrete was flowing down a pipe to make a section of wall, and, in between, recovered bentonite was running into another trench, where another Adiges rig worked. On a cleared portion of the site, ironworkers were assembling steel cages to reinforce the concrete. The cages looked like giant bedsprings, and when they were lifted vertically into the air by enormous cranes, sometimes as high as a hundred feet, and then dropped slowly—going, going, gone—into the wet slurry in the trenches, a crowd of bystanders usually formed at the fence around the site to watch.

At what had been the corner of Greenwich and Dey Streets, we came to a graded incline leading to the bottom of the excavation. We walked down, stopping often to let outsize yellow Euclid dump trucks labor uphill past us piled with loads of great boulders or rattle downhill empty after a trip across a temporary ramp under West Street to the cofferdam area. At the bottom of the incline, we crossed a plank over a lot of water and came to a large yellow drilling machine, which was slowly shattering rock. There was the smell of wet sand, and I noticed several varieties of pumps hard at work. We were seventy feet below the street, and, looking up, I saw for the first time finished sections of the new wall, excavated and exposed, with the ends of tiebacks sticking out in rows about ten feet apart. The top layer of tiebacks was in place, and workmen were drilling holes and inserting a second layer. To my surprise, the wall was not smooth and fresh-looking but, rather, full of lumps and quite scruffy, like a fairly well-preserved achievement of some much older civilization. I shouted as much to Kyle over the racketing noise of the drills. "We can chop off the lumps and put a masonry wall inside if we want to dress it up!" Kyle shouted back. "But it probably wouldn't be worthwhile for that section—it will be the garage!"

Kyle suggested that we return at midnight to visit the telephone vault, where one man from the Telephone Company would still be splicing wires in the last of the cables to be relocated. PATH traffic would be light at that hour, and when one tube was closed briefly for cleaning we could walk along the track and climb into the telephone vault from below, instead of descending through the manhole from the street. It would be somewhat wet, I was told, and to get out I would have to go up a vertical ladder connecting the vault's three floors—my least favorite form of exercise. Forewarned, I arrived clad in bluejeans and rubber boots as the clock hands reached twelve in PATH's control center, a basement room filled with dials and flashing lights to indicate the position of moving trains. I was handed a helmet, and we started out.

The trains were temporarily halted in the north tube, and we began walking down the tunnel. As I picked my way carefully through the mud and over the railroad ties, I was at the rear of a single file consisting of Kyle, Katz, and several officials from the Telephone Company and PATH. Red and white flashlights carried by the men ahead danced to the swing of their arms as we passed the arch of a spooky, abandoned side tunnel leading nowhere. I looked above me, wondering if I could see the curved top of the tube, but the darkness was a soft shroud. Although it was a hot July night, the air was cool where we were—about forty-five feet below the street, still in Manhattan but close to the riverbank. Kyle stopped for a moment to explain to me what I was about to see. The telephone vault, or manhole—three small, high-ceilinged rectangular rooms, one above another—was a watertight concrete box, which, like the Bathtub, was fastened to bedrock and built partly around the top of the PATH tube. When the vault was finished, a hinged segment of tube served as a trapdoor between the tunnel and the manhole.

Suddenly there was a burst of light. It came through this door, which led into a small, elevated concrete room, in which a man sat working with a large pile of tiny multicolored wires in his lap. He was wearing a yellow helmet, a blue flannel shirt, and a phone headset, but he pushed this aside to introduce himself as Charlie McQuade and to explain that there had been thirty-three splicers working six days a week in the area for the last five months but now he was the only one left. He was about to "throw," or splice, his last cable—one that had four hundred pairs of wires, or conversations, which meant eight hundred splices for him. The wires he was working on went to Philadelphia, Washington, Miami, and Moscow, he told us, adding that he could "throw" an average of two hundred a day. I had been told that splicing was one of the most highly skilled jobs in the Telephone Company, and as he talked and worked I could see why. If the wires weren't spliced with a tight pigtail twist, conversation on the line would be very noisy, and if a short circuit occurred there would be no conversation at all. Just then, someone called out that a train was about to come by. McQuade laughed. "Don't lean back too far, or you'll get a haircut," he said. We hurriedly climbed into McQuade's concrete room, the lowest of three in the vault, and, squeezing past him, we started one by one up the vertical steel ladder. On the second level, I paused to look at the telephone cables, which hung like large black hoses from ceiling to floor. Then I leaned down to see where I had come from. I could see the outer surface of the cast-iron tunnel tube, curved and heavy, with a dull-black finish, and if I had had any doubt about what it was, that doubt would have vanished a second later, when I heard a train rumble through. I started climbing again, and the air became increasingly warm as I neared the street surface. There was a sudden draft of wind from another train passing below, and as I held tight to the ladder I felt my helmet rise about a foot above my head. I grabbed for it, but it settled miraculously back, and I climbed out onto West Street to join the others. The Trade Center site was ablaze with light, and the rock crushers and drills were steadily pounding away.

Part of an engineer's professional skill involves finding ingenious and preferably cheap ways out of trouble, but the solutions for some of the Bathtub's difficulties were expensive. The tiebacks were so much more costly than anyone had expected that less expensive, buttress-style reinforcements were adopted for the base of the wall. Although the design of the tiebacks was supposed to protect them against corrosion from the stray electrical currents that always seem to be present in city ground, corrosion occurred anyway, mysteriously beginning with tiebacks on the third level below the surface. This was serious: if the corrosion persisted, and a substantial number of wires in the tiebacks failed before the inside floors were in, the walls would collapse. As it turned out, corrosion occurred in fewer than a dozen tiebacks, but the rest had to be constantly checked, and strain gauges were installed in the wall at points of known stress; a witch's brew of antifreeze and slurry was concocted to coat the wires that had been damaged. Bad leaks sprang up in the joints where the twenty-two-foot sections of wall came together, and a lot of dirt and water seeped in, contributing to the settling of the ground outside the site. The joints were hastily patched with rubber gaskets and cement. One day, Kyle got a hurry call to come to the corner of Greenwich and Liberty Streets. Workmen drilling into bedrock had suddenly found that they were digging into dirt and silt again. Kyle was fascinated by this phenomenon—an underground chasm in the heart of the city, probably dug out by the glacier. Another time, a crane operator who was filling in an old manhole kept on dumping dirt into what seemed a bottomless cavity, until Kyle's office received an excited message from PATH officials saying that part of the tunnel wall must have collapsed, because dirt was flowing over their railroad tracks. The crane operator had unwittingly dumped dirt into an access manhole to the PATH tunnel. After that, large flags at street level showed where the tunnel was.

When the two PATH tubes were exposed within the Bathtub, it was the first time direct sunlight had touched them since they had been built. They had been resting comfortably underground for almost three-quarters of a century at a steady fifty degrees Fahrenheit, and in the summer heat, which was over a hundred degrees, the iron began to expand. The engineers cut a slot about two inches wide in the tube to allow for expansion. At once, a PATH passenger called the Port Authority, in wild excitement, to report that the tube was breaking apart, so sheet metal was wrapped around the opening. After the tubes were completely in the open, the train engineers complained that there was a thundering noise as the trains passed through the tubes, which made the engineers think the exposed sections might be dangerous. They were told that the hanging, hollow tubes were simply acting like giant bass drums.

Around that time, I went down to watch the process of jacking up the tubes so that digging could be done beneath them for new tracks that would ultimately lead into the new station in the basement of the building. Meanwhile, of course, passenger service had to continue uninterrupted.

I found Jim Hastie, a young Slattery engineer, who was superintendent on the site for West Street Associates, standing in the bottom of the Bathtub, beside one of the two big black PATH tubes. He was wearing a silver helmet, which he kept removing to run his hand nervously through his short-cropped brown hair as he talked about steel saddles and trusses that would support the old tubes until new tracks were completed and the tubes removed. There was a low, rumbling noise, the ground shook beneath us, and a train passed through the tube, on which Hastie was casually resting his hand. He smiled. "I think this is the noisiest place in the world," he said. "I've got used to it, but I automatically talk as if everyone were hard of hearing." He went on, "This has been a bitch of a job. There has always been worry because of all the water. There was a hell of a lot of water in the ground before we got here, coming through the rocks from underneath, and we've had a lot of heavy rains, too. We're always having trouble with the pumps, which never seem to break down on a nice day. I forget whose law that is, but that's what happens. No matter how much experience you've had, water is a real unknown—water from the earth below and the heavens above. If it weren't for the water, we'd have been done long ago. If I had a penny for every gallon I've pumped out of here, I wouldn't be talking to you—I'd be in Hawaii." He took off his helmet and scratched his head. "So far, we've been able to cope with every one of our problems, thank the Lord. On other jobs, somebody has always known somebody who'd had the same problem before, but on this one there are no preconceived solutions—your approach has to be brand-new. You can't compare this foundation to any other—the PATH tubes, the slurry wall, the tiebacks, the size and depth of the hole, the nearness to the good old Hudson River. This is a fascinating job and an exasperating experience. You know you won't have one like it again, even if there are a lot of days when you're not too happy about being here."

A while afterward, I went to see Arturo Ressi, a tall, dark, thirty-year-old Italian engineer, who had directed the work of the Icanda crew. At the peak of Icanda's activity, Ressi had had about a hundred and fifty men on his payroll, but now there were only four, including him, and he was getting ready to leave. Now that the job was done, he enjoyed chatting about the Bathtub. He spoke of the terrible obstructions in the ground, which had produced "overbreaks"—the cause of the bumpy appearance of the Bathtub wall. Since all the work was done out of sight, there had been no way of checking on irregularities in the wall until excavation began. Time and again, he said, cavities left in the walls of the trench by the removal of boulders and other objects below ground would produce bumps and bulges in the wall after the concrete was poured. When excavation revealed the irregularity, the crew would smooth out the bumps as best they could, but it was impossible to achieve the even results Ressi preferred. Another difficulty, he said, was communication between highly trained specialists from Italy who spoke no English and the workmen on the site. "We found the curse words in Italian. On the job, we pointed and worked out words phonetically," Ressi said. "Communication was hazardous. But our men work all over the world and are used to making others understand certain things, no matter where they are."

Ressi's departure was a signal that the basic construction of the foundation walls of the World Trade Center had been completed; the only important step still to be taken was to release the tension on the fifteen hundred tiebacks and cut the exposed ends flush with the walls, leaving the buried portions underground. The other day I received word that this process had begun, and I went down to the Center for a visit with Francis Werneke, the present construction manager. His office is in the South Tower, now known as Two World Trade Center. The half-finished lobby startled me; the Italian marble that lined the walls and lofty ceiling was a shiny, stark white—the kind of stone I associate with a particular kind of ornate modern tomb, and there were crystal chandeliers and vertical strips of silvery metal.

On the twenty-first floor, Werneke, a very tall, cheerful man in a short-sleeved blue shirt and black-framed glasses, congratulated me on following the construction of the Trade Center's foundation for so long. Then he explained that all the tiebacks could be released when the temperature of the whole Bathtub area had been stabilized at seventy degrees plus or minus twenty degrees, which would permit a minimum of contraction or expansion of floor slabs.

He talked about the Bathtub: "That wall was put in the ground blind, with water lappin' on the other side at the same elevation that you can see at the Hudson River right across West Street. But if you go down seventy feet below the surface inside the Bathtub, it's all dry down there. As far as I'm concerned, the Bathtub is a miracle wall."

I looked out the narrow, slitted window at the Hudson River, and then I turned in the other direction and glanced down at the plaza below me. Workmen were filling in the surface with oblong stone blocks around the outline of a circular fountain, where a central sculpture was already in place, covered with a green tarpaulin. Soon the plaza would be transformed by shrubbery and hurrying crowds of people. If I come down here again in another couple of months, I thought, I won't even remember what the Bathtub was like.