Maybe the coolest thing about Ken Sagrestano’s job is that he gets to treat the busiest bridge in the world as his own personal swingset.

He swings from steel girders. He shimmies down ladders. On a sunny afternoon this week on the George Washington Bridge, Sagrestano pried open a steel manhole cover on the flat roof of the bridge. He climbed down and swung around, coming to stand directly on the bridge’s shoulder.

Beneath his feet, the forces at work bend the brain. Here, 600 feet above the Hudson River, the braided girders of the bridge’s western tower hold 22.5 million pounds of steel cable and decking up in the air. Up here, inside an enclosure called the saddle room, cables 6 feet in diameter flowed in a gradual arc over the tower’s thick, rounded grooves, all of it covered in thick gray paint and years of dust.

“It’s amazing,” said Sagrestano, who looked out of place on the bridge. Surrounded by workers carrying tools and heavy steel chains, he carried in his hands only the keys to his white Port Authority-issued Ford SUV.

The George Washington Bridge opened to cars on Oct. 24, 1931. In the intervening 87 years, its cables and suspension wires have supported the weight of millions of vehicles. They have resisted attack from the salty water of the Hudson River, and swayed in winds topping 70 miles an hour.

The bridge’s steel has resisted all the elements except one: temperature.

The deck rides high in winter, as its steel contracts in the cold. Then comes summer, when hot temperatures cause the entire mechanism to expand and sink.

All that salt, combined with the expanding and contracting, finally has caught up with the thing.

Age and salt have caused stress and corrosion to the suspender ropes, which tie the bridge’s four main cables to its double layer cake of roadways.

Now the Port Authority of New York and New Jersey, which owns and operates the bridge, plans to spend $1.9 billion replacing those suspenders. The agency also will rebuild roadways and helix-shaped bridges leading to and from the bridge.

This is harder than it sounds.

As the largest suspension bridge in the world when it was built, the George Washington Bridge does what it says: It suspends. It hangs in the air. It supports a gracefully thin curve of decking dangled between two muscular towers.

Now Sagrestano and Amanda Rogers, the lead engineer on the project, must re-suspend the bridge while it’s still suspended.

And because this is New Jersey and Manhattan we’re talking about, they must do it surrounded by traffic, on a bridge traveled by 280,000 vehicles every day.

“That’s the most important thing. The bridge must stay open,” said Rogers, whose spiky orange hair is nearly as bright as her yellow safety vest. “There’s very little space to work. So we have to stage everything very carefully to make sure we can do everything we need to do and stay on schedule.”

When this bridge was under construction in 1928, Bergen County was mostly farmland. Within a few years of its opening, the county became the most densely populated in New Jersey.

“Which is a remarkable change,” said Michael Aaron Rockland, a professor of American Studies at Rutgers University who recalled walking from his boyhood home in the Bronx across the bridge to camp in the woods of Fort Lee.

As the George Washington Bridge was built, huge sections of its twin towers were prefabricated. So, too, were sections of road decking. Cranes lifted both kinds of components into place.

Today, Rogers oversees work that looks remarkably similar, but on a smaller scale.

Everything workers need to re-suspend the bridge — from portable toilets and plastic sinks to Knaack-brand tool chests and braided lengths of cable that weigh several thousand pounds apiece — must be driven onto the bridge. From a closed lane of traffic, each piece is lifted by crane, swung over the steel sidewalk barrier and deposited on the sidewalk.

From there, workers carry their tools up one story to a flat-bottomed work platform suspended from the main cables. Heavier things like steel cables get winched up.

Walking the platform, one can see the work moving ahead in different stages simultaneously. The most important job is to replace the bridge's suspender ropes, which perform exactly as they sound. As suspenders hold up a pair of trousers, suspender ropes hold up the bridge, looping around the span's four main cables before dropping straight down into the bridge's innards, where they attach to steel girders.

The bridge has 592 of these ropes, and replacing them is a delicate slog.

"It's very repetitive," Rogers said. "With so many to replace we can't fall behind, because if we do it'll be very difficult to catch back up."

If weight is removed from one rope without proper balancing of all the rest, it might cause the bridge to tilt. That, combined with factors like wind and traffic, could lead to cataclysm.

To be safe, workers install two temporary suspenders before removing the first permanent one, Rogers said.These temporary ropes are to regular suspenders as Duane "The Rock" Johnson is to regular people.

They are jacked.

Their cables attach to their anchors by means of pins too heavy for an adult to lift. (I tried.) These pins hook into yellow I-beams, then descend into the bridge through thick steel sleeves with giant bolts jutting from their sides.

The rope work currently is happening close to the New Jersey side of the bridge. Closer to the middle, workers have removed thick steel casings from the main cables, revealing a massive cylinder made of about 28,000 wires. The outermost wires still retain the orange paint they received when the bridge was built, Rogers said.

Workers must assure that the wires deep inside these thick bundles are unbroken and free of rust. So on a recent Tuesday morning, a construction worker aimed a 10-pound jackhammer into the cable’s hide. The hammer pressed into place a white plastic wedge. Once a few of these wedges were inserted, a steel engineer poked his nose and fingers inside, inspecting the condition of every wire he could see.

“It’s still in great shape,” said Rockland, who authored a book titled "The George Washington Bridge: Poetry in Steel." “They take care of it like crazy.”

To make sure the cables remain rust-free, Rogers will oversee construction of an enormous dehumidifier. Using high-powered pumps at both ends of the bridge, the system will force air into the gaps between the cables and their sleeve-like casing, keeping the entire unit at a constant 40 percent humidity.

“It’s just like a dehumidifier in your house,” Rogers said, “but a lot bigger.”

Other changes will be more visible. At the four corners of the bridge's towers, engineers plan to add lookout stations. This will soften the 90-degree blind turns required of cyclists and walkers on the bridge’s two pedestrian walkways, allowing tourists and picture-takers to stand out of the flow of traffic. The current metal railing, which is about chest high, will be replaced by taller vertical steel slats to discourage people from attempting suicide from the bridge, Sagrestano said.

Those changes may only be visible to people standing close by, either on the bridge itself or from the Palisades in Fort Lee.

From farther away, the bridge will keep looking like itself. According to the original plans by its designer, Othmar Ammann, the steel skeleton was to be covered in concrete and then clad in granite, complete with stone statues. The goal was to make this big steel bridge resemble the much smaller Brooklyn Bridge, which has towers made of rock.

“Ammann wanted it prettied up,” Rockland said.

The George Washington Bridge was built during the Great Depression, however, so politicians including Franklin D. Roosevelt, then the governor of New York, decided to forgo the stonework and leave the skeleton exposed.

Ammann hated it. Others, including leading modernist architects like Mies van der Rohe and Le Corbusier, loved the bridge as the biggest expression yet that form can follow function.

“They considered the George Washington Bridge the most beautiful bridge in the world,” Rockland said. “At the George, you’re looking at the guts of the bridge all the time. You’re looking at exactly how it works.”

Over time, Ammann came around.

By the time he died in Rye, New York, in 1965, he considered the George Washington his favorite bridge of his long career. Ammann also designed the Throgs Neck, Bronx-Whitestone, Robert F. Kennedy-Triborough, Bayonne and Verrazzano-Narrows bridges.

He wasn’t alone. Even now, as the bridge will be carefully unbound and rehung, it inspires a certain kind of awe.

“I’ve always loved the George Washington Bridge,” Rockland said. “It’s always been my bridge.”

Email: maag@northjersey.com

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