“I knew I would never do anything, nor would I want to do anything, of this magnitude again.”

DAN TISHMAN Tishman/AECOM

In a construction first for New York City, Tishman/AECOM devised a two-story lightweight steel traveling system, called a “cocoon,” that eliminated the need for ironworkers to balance on beams and prevented tools and materials from blowing away in the wind. The cocoon, which contained work platforms, wrapped the tower’s upper limits in steel-framed, fire-resistant netting that draped down twenty floors. As the steel was erected, cranes raised the cocoon. Another ingenious move was building an internal seventy-story shaft up to the 100th floor so hoists could be used inside the tower to avoid shutting down an exterior hoist when winds exceeded 30 mph (48 kmh), as required by law. To allow core and curtain wall operations to proceed simultaneously, Tishman cantilevered a slider crane off the tower’s sloping northwest corner; this crane was used exclusively for concrete rebar and lumber. The slider traveled up just beyond the curtain wall.

Construction was staged in four tightly orchestrated sequences: steel framing, metal deck and concrete outside the core, concrete core shear wall, and concrete floor construction inside the core. The ironworkers who erected the steel preceded the other trades by eight to twelve floors. They were followed by the concrete workers. Fireproofing, curtain wall installation, carpentry, tiling, and a host of other services came later.

STEEL

All told, the superstructure consumed approximately 45,000 tons (40,802.4 metric tons) of structural steel. Ironworkers, the raising gangs who erect structural steel, loom larger than life. They are the royalty of the trades, the first to define the tower’s far borders, hundreds of feet above ground.

Four of the lead ironworkers—Field Supervisor Kevin Murphy, Foreman Kevin Scally, Connector Tom Hickey, and Connector Mike O’Reilly—have been working on the site since September 11, first helping with the rescue and recovery efforts and then, in 2006, once the tower’s substructure was completed, raising the skyline one beam of steel at a time. They’re big, tough guys doing arduous work, and as tenderhearted a group as you’ll ever meet. Each has touched every piece of steel in the tower. It’s hard to wrap your imagination around that fact, seemingly such a small thing, a touch, yet it says a lot about the building, which has been assembled by hand, and about them.

All of them belong to Local 40, the metropolitan region’s structural ironworkers union. They work for DCM Erectors, the firm contracted to erect the steel for the tower and its spire, the Transportation Hub, and Four World Trade Center. MRP, a company owned by the Davis Group, which also owns DCM, fabricated the steel.

Typically, a raising gang needs six workers to maneuver a piece of steel—the foreman; a hooker-on, who hooks the steel to the crane cable; a tagline man, who makes further adjustments; a signal man, who uses hand gestures or a phone to guide the crane, and two connectors, who place and bolt the beam into place. Before work on One began, however, the gangs had to assemble and “jump” the massive cranes used to lift the steel. Four cranes were used to erect the podium; after the twentieth floor, builders used two tower cranes. Before erecting the steel, they must “shake it out.” Shaking out is the process of sorting the steel, piece by piece, using hooks attached to the crane ball. The beams are then moved and placed upright at the location where they will be erected, an efficiency that saves time and makes erection easier. The beam weights vary from a few hundred pounds to forty tons (36.3 metric tons) each, while the podium columns weighed fifty tons (45.4 metric tons).

Two gangs, called North and South, raised the tower. A rivalry arose between them. “When there are two cranes, you want to race each other. Makes it more thrilling. It’s always a race,” the ironworkers say. Foreman Scally cautions, “A safe race.” Indeed, safety is the top priority—a worker can be thrown off the job for wearing ear buds, considered a distraction. On pace to complete one floor per week, the ironworkers were followed by a host of others, who plumbed, welded, and secured the beams.

On this job, Hickey and O’Reilly were the connectors. They have worked as a team for a long time. “We don’t have to communicate as much,” O’Reilly said. “He gives me a look and I know what the look means.” “Like husband and wife,” Hickey shoots back. Everyone guffaws. A strong sense of the gang’s family ties permeates the conversation. It’s in the blood, they say. O’Reilly’s father, who worked on the Twin Towers and the original 7 WTC, didn’t want his son to become an ironworker. Beyond the work’s obvious rigor, his father had fallen in 1985 while working on Seven and was paralyzed from the waist down. September 11, as O’Reilly recalled it, called him to the profession. He signed a beam, “This one’s for you, Pop.” Murphy is a third-generation ironworker, one of many in his family. He caught the bug from his father, a “rough and tough ironworker known as Cigar Murphy,” who taught apprentices, many of whom now work with his son. Hickey’s father also worked on the original towers. He is a fourth-generation ironworker on his father’s side and third-generation on his mother’s. “I do as my father did, as his father did,” he said. “I want to keep the name going. It’s pride in the family.”

Tom Hickey and Mike O’Reilly, two of the lead ironworkers, have been working on the site since September 11, 2001.

Similarly, in the tradition of their fathers and grandfathers, about thirty Kahnawake and Aquasasne from the Mohawk nation of Quebec walked the high steel at One World Trade Center. Renowned ironworkers, the Mohawks helped build the Twin Towers, the Empire State Building, 30 Rockefeller Center, and other major buildings and bridges in Manhattan.

When I asked the group what particular skills it takes to raise steel, I anticipated some modest mumbles about strength, balance, and courage. There was a long pause, as though they had never been asked this question before—though they are the very best in the world at what they do. Finally, one joked, “Well, you can’t be afraid of heights.” It’s a constant adrenaline rush. Are they afraid of falling? “You have to constantly be aware of where you’re at, but when you’re working, you’re in the zone,” O’Reilly said. “It’s second nature. You’re not thinking, ‘If I miss this step, I’ll fall.’ You have to think about your partner. Everything I do affects him.”

A typical day starts at 6:30 a.m. “We’re here seven days a week, sometimes twelve hours a day.” On site, conditions are hard, apart from the omnipresent winds and fifty pounds (22.7 kg) of bolts and wrenches they carry. “Weather-wise, we’re out in the cold, we’re out in the heat. It’s brutal sometimes. You just man up and do the work.” When it snowed, which it often did, dumpsters were hauled up into the tower and the ironworkers had to shovel off each beam and lift the snow into the dumpster. Then they chopped off the ice. If the beams were still icy, they used “‘rosebuds’ that shoot fire”—blowtorches—to melt the remaining snow and ice. On summer days, the steel sometimes got so hot that it couldn’t be touched. The work takes an extreme physical toll. “You’re lucky, when you retire, if you can walk,” Hickey said.

The erection of the spire segments, eighteen of them, was a milestone. Two raising gangs, a team of twelve ironworkers, erected the spire, along with the crane operators and those who prepped it. On a cold morning in January 2013, they hoisted the first segment, the heaviest segment, weighing more than sixty-seven tons (60.8 metric tons), into place. The rest of the segments followed in sixteen more trips. The last two segments were joined on the ground and lifted together. Scally and signalman John Collins assisted the four connectors—O’Reilly, Jim Brady, Tim Conboy, and Ryan Gibbs—who bolted the last piece, the beacon, into place on May 10, 2013. “It was an amazing day. There was a lot of relief when the spire was completed, and a lot of pride, which the entire city shared.” Asked if they’ll ever work on another building like this one, they shook their heads. “This one was special.” Despite the constant danger, excruciating work, and long hours, they said, almost in unison, “Twenty years from now, we will be able to look back and think of all the fun we had. We were blessed to do this work.”

“If we had a really boom-boom, perfect, summer, low-wind day, forty units would be a good day. We had one or two where we hit fifty, but that was a perfect storm of every condition working out.”

ROBYN RYAN Project Coordinator, Glass Curtain Wall, Benson Industries

CONCRETE

The specialized concrete mix used at One World Trade Center was made from local materials, including cement and stone from upstate New York. Making the concrete required nearly 200,000 tons (181,437 metric tons) of sand. It was quarried in Long Island, which, once the glaciers retreated twenty thousand years ago, was endowed with distinctive sand that has a combination of coarse and fine grains that is well suited for making concrete. Sand from the Port Washington peninsula, known as “Cow Bay sand,” was used to build New York City’s sidewalks and some of its most memorable skyscrapers, including the Empire State Building, Rockefeller Center, and the original World Trade Center.

These materials were moved by barge to the metropolitan area and then trucked to the Red Hook section of Brooklyn, where they were blended according to a customized recipe, stringently tested, and monitored. Steve Jackson of Eastern Concrete, which manufactured concrete for One and Three World Trade Center, as well as the Transportation Hub, said, “There were actually four cement products in each one of the mixes, as well as chemicals supplied by BASF. These mixtures were first of a kind, special mix designs just for this project.” Given the massive amounts of concrete needed—the tower consumed 208,000 cubic yards (159,027.4 m³)—materials were constantly replenished. “We received material anywhere from three to four in the morning until five to six at night, every day, just to keep restocked,” Jackson said.

Once mixed, the concrete was poured into the drums of Eastern’s fleet of trucks, and delivered to lower Manhattan in ten minutes. Pending traffic, of course. The plant’s close proximity was crucial for concrete of this strength, which cures quickly: if a batch could not be produced, delivered, and discharged from the truck in ninety minutes, it was no longer fit to use. Timing became even more urgent as the tower rose, since it took longer to pump the concrete to the upper levels. The small window of opportunity closed even more tightly during extremely hot or cold weather, since concrete also has temperature constraints. In the heat of summer, pours were planned for the cooler times of day. “At times we had to use ice to cool down the concrete to stay within the temperature specs. In the winter, we use heated water. When it’s 50 to 60 degrees, that’s the best time because it’s easier to maintain the temperatures,” Jackson said. And weather was not the only consideration. “As it sets and strengthens, concrete gains heat and produces heat. Even when you pour it in the wall, there are certain temperatures that must be maintained. The cooler you pour it, the more you hold down the temperature because it produces heat. Quite a bit of heat. When you’re pouring concrete in the summer and [air temperature is] 80 to 90 degrees, [the temperature of the concrete will] easily reach 150 to 160 degrees.” Radio Frequency Identification Devices (RFID) were embedded in the concrete to measure its internal temperature and to report on the maturity of the newly poured concrete, which facilitated early formwork removal and shortened construction time. What happens if the concrete inside the trucks doesn’t make it to the site on time? “You have to chop it out,” said Jackson.