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00:00:00The World Trade Center, two magnificent towers at the top of the world.
00:00:09The World Trade Center was the greatest project since the pyramids.
00:00:14It was structurally different from anything that had been done before.
00:00:17How the towers rose.
00:00:19If they can put a man on the moon, we can get this building up higher than 80 stories.
00:00:25And why they fell.
00:00:26Both towers took 10 years to build and 10 seconds to collapse.
00:00:33An engineering marvel.
00:00:35Going up 110 stories with steel.
00:00:38How do you do that?
00:00:40The challenge was to get down to bedrock without having it flood with water.
00:00:45Each floor was the size of an acre.
00:00:47200 elevators.
00:00:49It had its own zip code.
00:00:5030,000 cups of coffee are served daily.
00:00:52It was like its own little city within the city.
00:00:56It symbolized power and money.
00:00:59It symbolized bigness.
00:01:02The Twin Towers.
00:01:03Twin Towers.
00:01:04The Twin Towers.
00:01:05Twin Towers.
00:01:05Twin Towers.
00:01:08But from the beginning, warnings of what could go wrong.
00:01:13There was a three-alarm fire in the World Trade Center in New York City.
00:01:16The ad shows exactly where the plane would hit.
00:01:21They changed the design from six stairwells to three.
00:01:25All the steel in these buildings was lighter weight, which heats up enormously faster.
00:01:31And that turned out to be a huge element on 9-11.
00:01:34Sometimes you don't believe your own eyes.
00:01:39What just happened?
00:01:40Why did they stand and why did they fall?
00:01:43Was there something fundamentally wrong about the way that they built those towers that made them prone to collapse?
00:01:4920 years later, the real story behind an American icon.
00:01:54They were the builders.
00:01:55They were the makers.
00:01:57Wow, what a time to be alive.
00:02:00Nothing was beyond us.
00:02:01What a time to be alive.
00:02:31The seeds of the World Trade Center are planted a few miles from Manhattan
00:02:41at the 1939 World's Fair in Queens, New York
00:02:45with an exhibit built by the head of the Chase Bank, Winthrop Aldrich.
00:02:53China was supposed to have a display at the World's Fair, and they pulled out,
00:02:57and so there was an empty space.
00:02:59Winthrop Aldrich was part of a committee that decided to build a pavilion that was dubbed the World Trade Center.
00:03:07Winthrop Aldrich wants to exhibit trade goods from all over the world.
00:03:12It shows American optimism, American supremacy, American dominance of the world.
00:03:19Years later, after World War II, Aldrich tries to turn the exhibit into reality.
00:03:26It was going to be a 10-square block area with 21 buildings and thousands of different companies,
00:03:32but the idea was way too ambitious, too big to justify the construction of it, so it never happened.
00:03:38But in the mid-1950s, the idea is picked up by Aldrich's nephew, a rising young executive at Chase Bank.
00:03:46His name is his calling card, David Rockefeller.
00:03:51David Rockefeller was the youngest grandson of America's first billionaire.
00:03:55He felt it was his turn to come forward and put his own stamp on the city.
00:04:00It's around this time that David Rockefeller's brother has built Lincoln Center.
00:04:05His dad, John Rockefeller, has already built Rockefeller Center.
00:04:09Now it's David Rockefeller's turn, and he decides he's going to try a version of the World Trade Center.
00:04:15His early concept includes rotating exhibits, and much like the World's Fair would be a tourist attraction,
00:04:21the project will become the defining vision of Rockefeller's life.
00:04:32And so the first question was, where we should build a new building?
00:04:36Should it be downtown or in Midtown?
00:04:39And several institutions had already moved uptown.
00:04:45Midtown, which is where the big buildings were at the time,
00:04:48Reisler Building, Empire State Building,
00:04:50They're winning the real estate war.
00:04:52But David Rockefeller wants to build a new World Trade Center and revitalize downtown.
00:04:59And the reason is the financial business district was downtown.
00:05:03But Rockefeller quickly understands that to build something this ambitious,
00:05:07he will need powerful help.
00:05:09So what can we do?
00:05:11Let's think big.
00:05:12Downtown is the imperative, and that's where the chess games begin.
00:05:15The next move was going to have to be pulling in the Port Authority and using powers that they had.
00:05:23The Port Authority builds and operates the ports, bridges, tunnels, and airports in New York City and much of neighboring New Jersey.
00:05:30The Port Authority was enormously powerful because it had both the ability to raise unlimited amounts of money through tolls,
00:05:38and it had the power of eminent domain to take property and bulldoze what it wanted.
00:05:43It was almost its own state.
00:05:44The man who runs it is a New York power broker named Austin Tobin.
00:05:50Austin Tobin was incredibly diligent, incredibly smart.
00:05:54He used whatever he needed to use.
00:05:56Sometimes it was the raw power of the Port Authority, the money, the legal expertise they had that nobody else had.
00:06:04That's how Austin Tobin worked.
00:06:07Tobin quickly sees the logic of consolidating world trade under one roof.
00:06:11Back in those days, the business of world trade was concentrated in Lower Manhattan in a number of very small businesses.
00:06:21A steamship company over here, a freight forwarder over here.
00:06:25Here's the customs office over there.
00:06:27All these little companies scattered over Lower Manhattan.
00:06:30This is before fax machines and email.
00:06:33The paper had to be shuttled around with bicycle messengers.
00:06:36And so what if we had all these little companies under one roof, and we would literally have a center for world trade?
00:06:46Rockefeller woos Tobin.
00:06:48And soon, each realizes they need each other.
00:06:52With the power of the Port Authority behind it, the World Trade Center gains steam.
00:06:56The original plan for the World Trade Center would be located along the East River.
00:07:04But that plan isn't going to work for the Port Authority's other half, New Jersey.
00:07:10The governor of New Jersey objected, saying, no, wait a second, we're not getting anything out of this, and we're part of the Port Authority.
00:07:16And Austin Tobin says, well, what do you need?
00:07:20He said, I'm so glad you asked.
00:07:21Our New Jersey residents are employed in Manhattan, and they need reliable transportation.
00:07:27At the time, the Hudson and Manhattan Railroad carries thousands of commuters from New Jersey every day,
00:07:34via tunnels under the Hudson River, to a decaying station in Lower Manhattan.
00:07:38The railroad is falling apart.
00:07:41It's nearly bankrupt.
00:07:43And what we want you to do, Austin, take over the Hudson and Manhattan Railroad.
00:07:48Tobin takes a ride through it.
00:07:50Everything is falling apart.
00:07:51Rats are scurrying.
00:07:53Rails are screeching.
00:07:55There's a drunk on a bench, and the drunk kind of leans halfway over, looks at Austin Tobin, gives him a little wave, and then goes back to sleep.
00:08:02Yeah, and Tobin agreed to not only fix up the Hudson and Manhattan Railroad line, but merge it with this World Trade Center,
00:08:11taking the original project from the east side, and you would build the buildings on top of all this.
00:08:17A grand bargain is struck, and as a bonus, the future World Trade Center will now face the Garden State.
00:08:24The governor of New Jersey said, at least we can see the damn thing.
00:08:28Finally, David Rockefeller's vision is starting to take shape, but getting the World Trade Center built will require a tough-as-nails project director.
00:08:39Tobin finds his man in Guy Tazzoli.
00:08:42Guy Tazzoli feared nothing.
00:08:45If you met Guy Tazzoli face-to-face, one of the things that struck you is that he had this stare that he would stare you down.
00:08:53He was the one that controlled everything involving the construction, development, planning, operation of the Trade Center.
00:09:02With Guy Tazzoli on board, the project's concept will go from big to epic.
00:09:07Guy Tazzoli knew that the right way to sell a project and the self-image that Americans had, that this is the way it should be, we should be leading the world, they were going to have to go big.
00:09:16If you think about why America has this love affair with bigger is better.
00:09:22We have to put ourselves back in the mindset of the 1950s.
00:09:28The United States is the world leader in everything.
00:09:32We are what we are, big and powerful and mighty.
00:09:35Whether it was the size of the cars, whether it was jumbo jets, there was a bigger is better mentality.
00:09:42Bigger.
00:09:43And better.
00:09:44Bigger than life.
00:09:44Bigger is better.
00:09:46That's part of the American way of life.
00:09:48The largest construction project in the world.
00:09:50Being part of the generation that landed a man on the moon.
00:09:54Nothing was beyond us.
00:09:56The World Trade Center is about to become a reality.
00:10:01Building it will take a decade.
00:10:04You dig a trench, and you've got to keep that trench from collapsing.
00:10:10Test the limits of human ingenuity.
00:10:12And they came up with a method, which was a conceptual breakthrough.
00:10:18And require the ambition and work of hundreds of engineers, laborers, and artisans.
00:10:24It all begins with the work of one man.
00:10:28The architect.
00:10:29We choose to go to the moon in this decade and do the other things.
00:10:40Not because they are easy, but because they are hard.
00:10:45The Port Authority begins the search for the right architect to alter the New York skyline.
00:10:50And who they eventually choose surprises everyone, including the architect himself, Minoru Yamasaki.
00:10:57Yamasaki, they called him Yama affectionately.
00:11:01So they send him a letter.
00:11:03The Port Authority wants him to bid on this project.
00:11:07He gathers his staff around and he says,
00:11:08This shows you the importance of precision in business correspondence.
00:11:12Look how they've added a zero to the expected cost of this project.
00:11:17He was absolutely sure there was no way it could be higher than $28 million.
00:11:21But in fact, it was.
00:11:23It was budgeted at $280 million.
00:11:25And he basically said,
00:11:27Why the hell do you want me to do it?
00:11:29You know?
00:11:31He was a very unusual choice for all kinds of reasons.
00:11:35Minoru Yamasaki was not a wasp.
00:11:38He was not an Ivy League graduate.
00:11:41He was Japanese American.
00:11:43Not only that, his headquarters was in Detroit, Michigan, not New York.
00:11:48He also had not built a tower ever.
00:11:52Unless you call a 22-story building in Seattle, a skyscraper.
00:11:57Yama traveled to India, Italy, even to Saudi Arabia.
00:12:01I think that he saw an Arabic and Islamic arch that he really fell in love with.
00:12:07And that defined his architecture throughout his entire life.
00:12:12So Yamasaki goes out to New York and gave a presentation that knocked them off their feet.
00:12:18And they gave the project to Yamasaki.
00:12:22Yamasaki's office began to work with a model that would solve the problem of fitting 10 million square feet on the site.
00:12:32They tried over 100 projects with many, many iterations of nine buildings or four buildings.
00:12:39And they eventually focused on two towers.
00:12:42Immediately, people recognized that that was a really striking image.
00:12:48Twin towers that were exactly the same size.
00:12:51It symbolized power and money.
00:12:53It symbolized bigness.
00:12:56New York was so nice, they had to name it twice.
00:12:59So why not build two?
00:13:01The Twin Towers.
00:13:02Twin Towers.
00:13:03The Twin Towers.
00:13:04Twin Towers.
00:13:04Twin Towers.
00:13:05So Yamasaki went through iteration after iteration.
00:13:10One day, somebody tells him, you know, we're building the tallest building in the world.
00:13:15And Yamasaki, you know, he couldn't believe it.
00:13:19Nobody had told him.
00:13:20When Yama resisted getting the buildings higher than 80 stories, you know, guys said, we're going to put a man on the moon.
00:13:29And if they can put a man on the moon, we can get this building up higher than 80 stories.
00:13:33And that was that.
00:13:36After months and more than 100 designs, Yamasaki is finally ready to unveil his 110-story model of the world's tallest buildings.
00:13:45But there's a problem.
00:13:47They brought it over to Port Authority headquarters to show it off.
00:13:51It wouldn't fit in the room.
00:13:53It was too tall for the ceiling.
00:13:54And they tried to lower it, you know, and nobody could figure out how to do that.
00:13:57And somebody ultimately just went up and punched out a couple of ceiling tiles.
00:14:02I was part of the entourage that was there at the time that Yamaha showed up.
00:14:07Always an interesting experience.
00:14:11Very shortly, you're going to have a great thrill when you see the actual design.
00:14:15And plan for this great center.
00:14:17Thank you very much.
00:14:21To make room for such a massive project, something else has to go.
00:14:27The master plan for the World Trade Center was to erase 14 city blocks of the historic grid of New York.
00:14:34Part of that were commercial buildings called Radio Row.
00:14:40These were small shops.
00:14:42They were in the business of selling radio tubes, television sets off the shelf.
00:14:46The Port Authority invokes the power of eminent domain, condemning the neighborhood and forcing out businesses.
00:14:55They held rallies.
00:14:57They hauled coffins down the street and put placards that said, here lies Mr. Small Businessman.
00:15:04Eminent domain is the card that Austin Tobin brings.
00:15:09The wrecking ball came and just knocked down Radio Row and, you know, just blink of an eye.
00:15:13But the World Trade Center faces opposition from a much more powerful force, Lawrence Ween, perhaps not coincidentally, part owner of the tallest building in the world, the Empire State Building.
00:15:26This is a battle among real estate titans in New York City.
00:15:31The snow holds barred.
00:15:34Lawrence Ween takes out a full page in the New York Times.
00:15:37His ad showed an airliner plowing in to the North Tower.
00:15:42In an uncanny coincidence, the image shows almost exactly where the plane actually would hit on 9-11.
00:15:53In fact, the Port Authority has concerns about a jetliner colliding with the towers and even studies the possibility.
00:16:00Frank DiMartini was a staff architect.
00:16:03He was asked about the possibility of an airplane crashing into the twin towers of the World Trade Center.
00:16:09The building was designed to have a fully loaded 707 crash into it.
00:16:15I believe that the building probably could sustain multiple impacts of jetliners.
00:16:22Frank DiMartini's analysis was correct.
00:16:25He's working on the assumption that you have a 707, which is a relatively small sort of jumbo liner.
00:16:32What Frank DiMartini was not asked, and nobody was asking back in those days,
00:16:37what if it was a terrorist attack by a jumbo jet, which was full of fuel?
00:16:45Lawrence Ween's ad talked about an accident that might happen.
00:16:51It was about both money and ego.
00:16:53His intent was to stop the project.
00:16:56And he tried to block it, and he failed. He couldn't block it.
00:16:59You know, it's a New York fight. Somebody's got to win, and somebody's got to lose.
00:17:04Despite any fear or resistance, the Port Authority moves ahead with plans to break ground.
00:17:10Immediately, they face another obstacle, and the only solution is to re-engineer the island of Manhattan.
00:17:34Manhattan is just an amazingly appropriate place for the construction of high-rise buildings.
00:17:41Much of the island has super strong rock called Manhattan Schist.
00:17:47But the World Trade Center site, though, the Manhattan Schist is deeper than in other places of the city.
00:17:53But also, we are really very close to the Hudson River.
00:17:56The challenge was to find a way to get down to bedrock to build your foundation without having it flood with water.
00:18:05So, how do you do that?
00:18:07Well, you've got to build a box.
00:18:08On top of the box, you could build the towers.
00:18:12And that box, those walls, have to be, first of all, watertight.
00:18:15And they have to be supported so that the soil behind the walls doesn't collapse the walls.
00:18:20And they came up with a method, which was a conceptual breakthrough, the slurry trench method.
00:18:26You dig a trench 50 to 60 feet deep, and you've got to keep that trench from collapsing.
00:18:32So, you pump something called slurry, which is bentonite.
00:18:35It's like a mud.
00:18:36And now you've got this trench filled with bentonite slurry, and you lower a steel cage into the bentonite.
00:18:42And then you fill that trench with concrete.
00:18:45And as the concrete goes in, bentonite is lighter.
00:18:48The bentonite comes out.
00:18:50And you capture the bentonite, and you put it in the next trench.
00:18:54And eventually, you wind up with a wall that's totally submerged.
00:18:57You have four walls that are built that way.
00:18:59And then dig the dirt out.
00:19:01And as you dig down, you drill behind the wall, and then you lower a cable, anchor it into rock.
00:19:07And you have a stable wall so that it wouldn't cave in.
00:19:11We affectionately called it the bathtub.
00:19:14This is a bathtub that keeps the water out, not the water in.
00:19:18And now you can remove the dirt, and you can build your skyscraper.
00:19:22When they started excavating, they found anchors.
00:19:28They found parts of ships.
00:19:30We found things like cases of 300-year-old grog, which the laborers drank.
00:19:35We stopped them, but they were drinking it for lunch.
00:19:38But realize that also running through this bathtub were two tubes that the trains ran through.
00:19:43And there were 50,000 commuters a day that came into Lower Manhattan on those trains.
00:19:49So we had to maintain that no matter what.
00:19:51It was handled like an eggshell.
00:19:53You couldn't afford to crack that.
00:19:54When I went to the Trade Center in 1968 as a young field engineer, we were just starting the excavation of the bathtub itself.
00:20:04Believe it or not, the first thing that struck me was the size of the Euclid trucks.
00:20:09These huge yellow dump trucks that held, oh, I don't know how many yards.
00:20:15They must have held 50, 60 yards of dirt.
00:20:18And the tires were bigger than I was.
00:20:19It was emblematic of what the site was all about.
00:20:23It was huge.
00:20:24It was, you know, 16 acres of construction in the middle of Manhattan.
00:20:28You know, every trade imaginable was there.
00:20:31There was a field office with engineers in it, working, you know, feverishly to resolve engineering problems.
00:20:37And they were still designing during the construction of the Trade Center, structurally designing.
00:20:42So it was a huge laboratory.
00:20:44We had just gone to the moon.
00:20:48And I thought, oh, wow, what a time to be alive.
00:20:52Nothing was beyond us.
00:20:56Guy Tazzoli was a very creative man.
00:20:59His ideas came to him, he believed, when he was shaving.
00:21:02As the story goes, he came in one day and said, I was shaving this morning and thought, what are we going to do with all this dirt?
00:21:08The thought was, well, dump it in the Hudson River.
00:21:10And, of course, his staff says, you can't do that.
00:21:12Guy said, well, let's engineer it so we can create more land in lower Manhattan.
00:21:17And then that was the beginning of Battery Park City.
00:21:20More than 23 acres of land which was donated to the city of New York.
00:21:25The next move, actually building the World Trade Center, will require new ideas and new technology.
00:21:31It was a structural system known as a tube.
00:21:36Hundreds of design and engineering decisions are about to be made.
00:21:39All of the systems in the building were unique.
00:21:43And some of them will have terrible, unforeseen consequences for the future.
00:21:47This whole concept of as much open space as possible, it's a dream.
00:21:52But they're not too safe in a fire.
00:21:54To meet the unprecedented challenges of constructing the World Trade Center, the Port Authority hires Leslie Robertson, a brilliant young engineer.
00:22:11You might say in layman's terms, Minoru Yamasaki was the artiste.
00:22:17But the nuts and bolts, that's the responsibility of the structural engineer, Leslie Robertson.
00:22:23The first thing Robertson and the architect must do is figure out how to satisfy one of their client's biggest demands.
00:22:30Creating an unprecedented 43,000 square feet of rentable office space on each floor.
00:22:36The traditional way of building a skyscraper was with a lot of interior columns.
00:22:44Tenants do not like interior columns because it cuts down on their use of the space.
00:22:51So one of the breakthroughs that Minoru Yamasaki and Leslie Robertson came up with was to put the bulk of the strength of the building in the outside.
00:23:00It was a structural system known as a tube structure.
00:23:09Unlike the traditional building, some of these columns that would otherwise be on the interior have been shifted out to the perimeter of the building.
00:23:17A good way to think about it is the Twin Towers resemble two stalks of celery.
00:23:23The rigidity comes from the outside.
00:23:25The result was you have a great deal of rentable, usable space in the middle.
00:23:31Each floor was 208 feet by 208 feet, about the size of an acre.
00:23:36And that's the beauty of a tube system.
00:23:41But there's a new challenge.
00:23:43Each tube is built with heavy steel.
00:23:45So engineers need to find a way to keep the buildings as light as possible.
00:23:49Rigid columns at the core.
00:23:52You have the rigid columns at the perimeter.
00:23:54That's pretty heavy steel.
00:23:56But one way that you can make things lightweight is in the floors.
00:24:01Each floor was supported by truss construction.
00:24:06The floor system was comprised of trusses, a metal deck, supporting concrete slab.
00:24:13Floor trusses extend from those exterior walls to an interior core.
00:24:22Building the World Trade Center required so much steel, it was shipped in from as far away as Japan.
00:24:28At one point, they were trying to deliver steel from Jersey City to Lower Manhattan to construct the Twin Towers.
00:24:35There was a tugboat strike.
00:24:37And they were frustrated because they needed to get these huge pieces of steel from Jersey City to Lower Manhattan.
00:24:45And there was a particular piece of steel that they needed that was too big to be transported by truck.
00:24:50So they came up with this innovative idea that they would try to transport it by means of helicopter.
00:24:58So you have a long cable attached to this piece of steel.
00:25:01But what they didn't reckon on was as the helicopter is moving along, this piece of steel was starting to sway.
00:25:10And it produced too much torque on the helicopter.
00:25:13And when they got about halfway across the Hudson, they had to cut the cable and drop the piece of steel because otherwise the helicopter would have crashed.
00:25:22And so to this very day, that piece of steel rests on the bottom of the Hudson River.
00:25:28It's never been recovered.
00:25:30The next challenge, how to hoist all that steel.
00:25:34Even the tallest cranes in the world aren't tall enough for this task.
00:25:38Going up 110 stories with steel, how do you do that?
00:25:42It turned out that engineers in Australia had solved this problem with a self-contained crane, which was nicknamed the kangaroo crane.
00:25:53The crane would lift itself up by its own pistons under it and jacking beams.
00:25:57And the crane would actually rise.
00:26:00It could jump 12 feet at a time.
00:26:02And when they finally got up to the 110th floor, the engineers took it apart and sent the parts down the elevator.
00:26:09But the Port Authority needs to know, how will slender, lightweight towers stand up against New York City's hurricane-force winds?
00:26:21Common sense might say, well, okay, just build it very sturdy and it won't sway in the wind.
00:26:28But actually, you have to figure out how much can you allow the building to flex without the building collapsing.
00:26:34So engineers set out to determine how much the World Trade Center will sway.
00:26:39In 1964, they commissioned a wind tunnel study, one of the first of its kind for a skyscraper.
00:26:47They were subjected to winds of 180 miles an hour.
00:26:51The wind tunnel study revealed that the towers were very lively.
00:26:55They discovered that the towers might sway as much as 10 feet in high winds.
00:27:00There's also the psychological side.
00:27:03You need to know how much sway will a tenant tolerate.
00:27:08Knowing that people sense sway with their eyes, the Port Authority commissions another study in secret.
00:27:14So what they did is they put an ad in the local paper that said, free eye exams.
00:27:21They had an eye chart up on the wall and, you know, people would come in and it's like, free eye exams, okay?
00:27:27The eye exams would take place in a building sitting on hydraulics.
00:27:33They would start to sway the building without telling the people.
00:27:38To their dismay, all they had to do was sway it out a very short distance.
00:27:43And people all of a sudden say, you know, I'm not feeling very well.
00:27:47The experiment told them that they were going to have to stiffen up their building considerably.
00:27:51Or as Les said, it was going to be a billion dollars right down the tube.
00:27:55So what was done was the introduction of viscoelastic dampers.
00:28:04And they acted like shock absorbers.
00:28:07And there were 10,000 of these in each tower.
00:28:11And now the World Trade Center could sway as much as 3 feet at the top.
00:28:15That sounds like a lot, but these were really tall buildings.
00:28:18Basically, the upper three stories of the tower had trusses spanning from the exterior walls to the core and beyond to the next exterior wall.
00:28:38And then in both directions.
00:28:41And so what those trusses did is they linked the perimeter tube to the core.
00:28:48Each of the twin towers were designed to have a broadcasting tower built above the roof.
00:28:56And the hat trusses were designed to support these broadcasting towers.
00:29:02The thing about the hat truss that was structurally significant, and Les knew this,
00:29:08was that if something happened to the exterior columns, the stress from that would pass over and it would be carried by the interior columns.
00:29:17In other words, they sort of protected each other.
00:29:19It was another way that the building became more stiff.
00:29:21It didn't sway as much because you were gluing pieces of it together rather than letting them ride around separately.
00:29:28And that was a huge problem they had to solve with buildings this tall and this flexible.
00:29:32The hat truss, of course, by its mere presence, contributed to the stiffness of the building.
00:29:38But the design of the towers would have been perfectly fine even without it in terms of their ability to counter hurricane winds.
00:29:49But on 9-11, the hat truss played a role that they were never designed for, and it turned out to be a life-saving role.
00:30:02While sway might be a nuisance, the Port Authority faces a problem far more troubling, one that will have tragic consequences decades later.
00:30:10One of the crucial things about high-rises is to figure out how to consider the effect of a fire.
00:30:16Now, the practice of putting very, very, very light steel into the floor trusses, it's important to raise questions about having a totally reliable fireproofing system.
00:30:29Almost all the steel in these buildings was lighter weight.
00:30:34Lighter weight steel heats up enormously faster than heavy beams and columns.
00:30:42Enormously faster.
00:30:43That plays a role as to when the steel starts to fail, you know, in a fire, because as it becomes softer and softer and softer, and these little trusses on the floors, they heat up faster, and so they're going to be more prone to heat.
00:30:56Also, this whole concept of as much open space as possible, it's a dream, but they're not too safe in a fire.
00:31:04Because there's nothing in your way.
00:31:05And these fire safety issues are made even worse, thanks to a mafia connection.
00:31:12Louis de Bono was the head of a company that was hired to do fireproofing for the World Trade Center.
00:31:17It seems that the company was corrupt.
00:31:20It was part of a crime family.
00:31:22In those days, it was hard to get anything done of any scale without crossing paths with the mob.
00:31:28It seemed that he was skimming off some of the money that should have been turned into his crime boss.
00:31:35John Gotti.
00:31:38Eventually, Louis de Bono was found killed gangland style in the garage of the Trade Center.
00:31:45Louis de Bono's company was taking shortcuts with the fireproofing.
00:31:50He, at times, simply sprayed the fireproofing on, and it was just flaking off.
00:31:54It was not robust enough.
00:31:55It was not thick enough on the floors.
00:31:57It was not thick enough on the core columns, and it was not strong enough.
00:32:00So if you're going to choose lightweight steel, you better have the fireproofing.
00:32:04Because if something extraordinary happens, and, you know, statistics say that that happens every now and then, it's Murphy's Law, you're going to face this situation, you better be prepared.
00:32:14And that turned out to be a huge element on 9-11.
00:32:18Constructing the world's tallest buildings requires new thinking.
00:32:27Almost everything that goes into the World Trade Center's design is original.
00:32:32From the very beginning, what made these two towers so significant was the audacity that it took to plan and build them.
00:32:40There were so many innovations, many of which continue with us to this very day.
00:32:46The one that's most significant is the elevator system.
00:32:51Before the Trade Center was built, they felt you couldn't go beyond about 80 stories.
00:32:57The more stories, the more people.
00:33:00The more people, the more elevators.
00:33:02As you go up higher and higher, you need more elevator shafts.
00:33:06And all of a sudden, the elevator shafts take up the entire footprint of the building.
00:33:11The Port Authority finds its innovative solution underground.
00:33:15Well, the way the New York City subway system is designed is you have major terminuses where express trains stop and then they get on the local.
00:33:24Same thing with the World Trade Center.
00:33:26The towers would be organized into three zones served by express elevators.
00:33:30Local elevators would run within each zone.
00:33:33In between the floors is something called the sky lobby.
00:33:36They get off at the sky lobby and they go to the local elevator banks to go to their floors.
00:33:40But then they said, people will never rent space in the building.
00:33:45They're not going to change elevators to get to their floor.
00:33:48But Geith has always said, as long as they're moving, they're not even going to know the difference.
00:33:53And that's exactly what happened.
00:33:55With a radically new elevator design in place, engineers face a new issue.
00:34:02Unlike many earlier skyscrapers, the narrow windows running up the sides of the towers don't open.
00:34:08The temperature in the tower would rise 20 to 25 degrees above the outside temperature.
00:34:13How do you cool 10 million square feet of office space?
00:34:16The solution, they discover, sits right outside those windows.
00:34:20The World Trade Center had to take the water in from the Hudson River, circulate it through a system that would extract the heat from the building,
00:34:29and put it into that water and push it out into the Hudson River.
00:34:33There was nothing like that anywhere in the world.
00:34:35You had 60,000 tons of air conditioning capability.
00:34:39You could air condition the suburbs of Cleveland with the total capacity that was in the Trade Center.
00:34:45The tower's windows are another engineering marvel, consisting of 43,600 sheets of narrow glass.
00:34:52The windows on the World Trade Center were rather narrow.
00:34:57It was part of the design.
00:34:58Minoru Yamasaki had a fear of heights himself.
00:35:02He also wanted to minimize the risk to the window washers.
00:35:06Everything about this project has to be special.
00:35:09And the window washing system was a robotic window washing system.
00:35:15I spent a lot of time with Rocco Camage, and he said it was kind of an ideal job because with these automated machines,
00:35:22it would take about 30 minutes for the machine to watch one column of windows.
00:35:28And during that 30 minutes, he could pretty much relax and enjoy the view.
00:35:3220 minutes going down washing, slow speed.
00:35:3710 minutes comes up on fast speed.
00:35:40But it isn't all relaxation for Rocco Camage.
00:35:47Between the 107th floor and the 110th floor, the windows are wider.
00:35:53And for these, there is no machine.
00:35:55He has to be strapped in and wash them by hand.
00:35:59It takes a certain nerve.
00:36:00Not anyone can do that.
00:36:05In April 1973, the World Trade Center officially opens.
00:36:10I want to extend my special compliments and appreciation both to the Port Authority and to Mr. Yamasaki himself personally and their whole firm for the creation they have brought here.
00:36:30The ceremony celebrates a decade of architectural and engineering achievement.
00:36:35But at first, the buildings are unpopular and considered an eyesore.
00:36:40Initially, there were only a couple of tenants.
00:36:42The buildings were largely occupied by government agencies because they couldn't get commercial customers down there.
00:36:47I think there were a lot of fears moving into the Trade Center.
00:36:50I mean, it was just so high.
00:36:52People had doubts.
00:36:53Working in the World Trade Center, especially in strong winds, snow, like, you could feel its sway.
00:37:03You could feel the movement almost as if you were on a ship.
00:37:08And in high winds, you could actually hear sounds.
00:37:10Sort of a low groan.
00:37:19It reminded me of being on board ship when I was in the Marine Corps.
00:37:22If you went into the bathrooms, the waters in the toilet bowls would be moving from side to side.
00:37:29It was clearly evident.
00:37:34Because of some of these fears, it didn't do very well at first.
00:37:37And all the negative predictions regarding the glut of office space and people not wanting to work in high buildings, it all seemed to come true.
00:37:46It looked like a white elephant.
00:37:47It really did.
00:37:50To make matters even worse, a blockbuster disaster film heightens fears of giant skyscrapers.
00:37:56The world's tallest building becomes the Towering Inferno.
00:38:06Then, just two months after the movie's release, life imitates art.
00:38:11There was a three-alarm fire early today in the 110-story North Tower of the World Trade Center in New York City.
00:38:18Many people who saw the fire were reminded of the movie picture, The Towering Inferno.
00:38:22Sixteen firefighters are injured, and the media quickly highlights a problem.
00:38:27The Trade Center's windows are sealed, and there are no sprinklers in the building.
00:38:31The fire commissioner said, I'd sleep a lot better at night if the World Trade Center had sprinklers.
00:38:37The Port Authority installs a sprinkler system that will be severely tested on 9-11,
00:38:42as will another unique feature of the towers, its stairwells.
00:38:47Here's the thing about the stairwells.
00:38:49They were clustered in the middle.
00:38:50Again, this whole concept of as much open space as possible.
00:38:55Clustering the stairwells makes them more vulnerable in case of fire or an attack.
00:39:00But just as important as the stairwells' location is their number.
00:39:04At the time the World Trade Center is planned, city building code requires six stairwells.
00:39:09But the Port Authority is exempt from local codes,
00:39:12and, after careful study, chooses to follow a newer standard that isn't yet law.
00:39:18And so they cut it from six stairwells to three.
00:39:22They were like, great, we can get more real estate.
00:39:25And so they changed the design in the middle of the planning for the construction of the towers.
00:39:29And that's something that had impact on September 11th.
00:39:32So it was not an auspicious opening for the building.
00:39:40It got terrible reviews architecturally.
00:39:43Ada Louise Huxtable was the most powerful architecture critic in the country at that time.
00:39:48She was highly critical.
00:39:50Ada Louise Huxtable wrote,
00:39:51Who's afraid of the big, bad buildings?
00:39:55Trade Center towers could be the start of a new skyscraper age,
00:39:58or the biggest tombstones in the world.
00:40:03The World Trade Center seems destined to remain a failure.
00:40:07But the tide of history is about to turn.
00:40:10I stop my car, and I look up.
00:40:12My heart was in my mouth.
00:40:14Oh my God.
00:40:15It's 1974.
00:40:22The newly opened World Trade Center is a critical and popular disappointment.
00:40:26People are afraid of the complex, and few tenants are moving in.
00:40:30It was too big.
00:40:31It was too expensive.
00:40:33It was too wasteful.
00:40:34The Port Authority had a terrible public relations problem.
00:40:39And then one day, something happened.
00:40:42I remember that day like it was yesterday.
00:40:44It was August 7th, 1974.
00:40:49And I was driving into the building.
00:40:52It was around 7 or so in the morning.
00:40:55What the heck happened?
00:40:56What's going on?
00:40:58I stop my car, and I look up.
00:41:04It's a guy with tightrope walking.
00:41:05Oh my God.
00:41:07He was a Lee Petit, who was a tightrope walker.
00:41:10I could see him from my office on the 66th floor.
00:41:13He stood on the wire.
00:41:14He walked back and forth, 1,350 feet in the air.
00:41:18He danced.
00:41:18He jumped.
00:41:19He laid down.
00:41:22My heart was in my mouth.
00:41:24I thought he was going to fall.
00:41:25They called Guy Tazzoli.
00:41:26He had a police radio in his car.
00:41:28But he says, make sure he don't fall.
00:41:31You know, that was, what are you going to say?
00:41:36Guy Tazzoli said, you are not going to arrest him.
00:41:39This is the greatest piece of publicity that we've ever gotten.
00:41:42Why did you do this?
00:41:43There is no wire.
00:41:44Just because when I see a beautiful place to put my wire, I cannot resist.
00:41:49Instead of just talking about what the perp did, the officer just was amazed.
00:41:54Supreme, the apex of excitement.
00:41:57Jeez, I want to go up to the tower and see what he saw.
00:42:00This was the beginning of the love affair with the World Trade Center.
00:42:03Even King Kong, who once helped establish the Empire State Building as an icon of New York
00:42:12City, now switches his allegiance to the Twin Towers.
00:42:16It certainly brought attention to the towers.
00:42:18It said to the public, you don't have to be fearful of these looming structures.
00:42:22Come down and embrace the towers.
00:42:27The South Tower, you had the observation deck.
00:42:30It was a real hit with working class people.
00:42:33Joe Sixpack can take his family, take their out-of-town friends, unbelievably affordable.
00:42:40Tazzoli insisted on this.
00:42:41Meanwhile, on the North Tower, you had this elegant Windows on the World restaurant, which
00:42:50was very expensive.
00:42:51It became the largest grossing restaurant in the world.
00:42:55The panoramic view is a result of an earlier battle waged by Guy Tazzoli and the Port Authority.
00:43:08Guy goes on to the project, Windows on the World, and he says, we cannot have a restaurant
00:43:15on the top floor of this building when you can't see out the windows.
00:43:19So he came up with a concept to widen the windows on the 107th floor of both towers.
00:43:26Yamasaki went berserk.
00:43:29You can't do that.
00:43:30You know, you destroy the aesthetic of the building.
00:43:33People will look up, and Guy says, it's a quarter of a mile up.
00:43:37You can't even, you can't see it.
00:43:39But Yamasaki goes to Austin Tobin and threatens to quit.
00:43:42So Austin Tobin calls Guy into his office.
00:43:47Guy says, well, if you don't do it, I'm quitting.
00:43:49So this went on for about a year, back and forth and back and forth, changing the steel
00:43:56on the 107th floor.
00:43:57And it was a million dollar extra in both buildings.
00:44:01Anyway, long story short, they widened the columns.
00:44:04They widened the windows, you know, so that you could see out the window.
00:44:08Down the road, now windows is open, and Jamo was sitting at one of those tables, and he's
00:44:14looking out, looking around, and he calls Guy over, and he says to him, whispers, not
00:44:19in front of him, he whispers in his ear, you were right.
00:44:22You know, you were right.
00:44:23The view from windows on the world was just spectacular.
00:44:28We were 107 stories in the sky, overlooking the most beautiful city in the world.
00:44:38Suddenly, the World Trade Center became almost fully occupied.
00:44:4350,000 people work in these buildings.
00:44:46There were a lot of high prestige clients in there.
00:44:48It had a panache to it.
00:44:49It was like its own little city within the city.
00:44:52It had its own zip code.
00:44:53It had its own police.
00:44:54200 elevators, 200,000 tons of steel.
00:44:5830,000 cups of coffee are served daily.
00:45:00It sat there at the tip of Manhattan and said, there's nothing like me, and there never will
00:45:05be, and I'm not going anywhere.
00:45:08People have often asked me, how did the Twin Towers become targets?
00:45:13They're right next door to Wall Street, and what does Wall Street represent?
00:45:18It represents American capitalism.
00:45:21The whole world doesn't feel affectionate about that.
00:45:25Some saw the World Trade Center as an emblem of power, and we're going to bring it down.
00:45:30We're going to show they're not so mighty.
00:45:32And so, when you build a tall building, it's almost like you're asking for it.
00:45:42February 26, 1993.
00:45:46Is a cold, blustery day in New York City.
00:45:50All of a sudden, the whole tower heaved.
00:45:54And it was almost as if the building just had this jump or shudder.
00:46:02Pandemonium at New York's World Trade Center.
00:46:04After a powerful explosion, rescuers are evacuating thousands of people from the 110-story Twin Towers.
00:46:10There's fire, and there's smoke.
00:46:13It is billowing up through the World Trade Center.
00:46:15We decided that we would have to evacuate to a stairwell in heavy smoke to begin to exit the building.
00:46:27You're watching them spill onto the street.
00:46:31Coughing and hacking.
00:46:33Their noses covered with black soot.
00:46:38It's ridiculous!
00:46:40Imagine a situation where there's no lighting.
00:46:43Tremendous amount of dark smoke.
00:46:45What we did was essentially form a small human chain with some flashlights and guide people to the stairwell.
00:46:53The stairs were filled with people.
00:46:56And with hand on the shoulder of the person ahead of you, for two hours, we went down the stairs.
00:47:07There was no hope whatsoever.
00:47:10No communication at all.
00:47:11The only alert that we had was the smoke coming in.
00:47:14Get the gas turned off in the street.
00:47:16Connets on the way?
00:47:17Yeah.
00:47:18They gathered the troops together.
00:47:19The governor, he said, well, you're the guy I'm going to fire.
00:47:21How could you not control a transformer explosion?
00:47:24And I said, governor, hold your judgment until you see it.
00:47:27We were concerned about the slurry wall since the floors had collapsed.
00:47:31The governor, he saw it, and he said this was a bomb.
00:47:34I said, yeah.
00:47:34No kidding, governor.
00:47:35It was a bomb.
00:47:36The United States Department of Justice is operating on the assumption tonight, on the theory that this was the work of terrorist bombers.
00:47:45A rental van loaded with a fertilizer bomb entered the B-2 level of the parking garage under the North Tower.
00:47:52The explosion ripped through four basement levels with a force of more than 1,200 pounds of dynamite.
00:47:57The truck was post near the corner of the building.
00:48:01The terrorist plan was to have one tower fall into the other tower like a row of dominoes.
00:48:07What they didn't reckon on was the great strength of the column.
00:48:11It didn't collapse.
00:48:13It wasn't broken.
00:48:14The bomb was planted by a radical Islamic terrorist cell with ties to Osama bin Laden.
00:48:23The Port Authority works around the clock to repair the damage and make design adjustments that will prove critical on 9-11.
00:48:31In 93, it took us almost 11 or 12 hours to evacuate the towers entirely.
00:48:37We learned a lesson from that.
00:48:39They implemented things like emergency lighting in the elevators, luminescence stripping in the stairwells,
00:48:45more extensive communication with tenants about fire hazard and fire evacuation.
00:48:50But with only six fatalities and the towers quickly back in business, the warning signals are overlooked.
00:48:56The fact the towers stood perhaps gave people license to believe that we were invulnerable.
00:49:02We should have seen that there was more to come.
00:49:04In fact, one of the terrorists makes it clear what incredible challenges the Twin Towers
00:49:12and every innovation and design choice that went into their construction will once again face.
00:49:17Ramzi Youssef, who is the mastermind of the terrorist attack, said at his trial in 1997,
00:49:23if it takes us a thousand years, we will topple these evil towers.
00:49:27That was part of his statement before the judge, before he was sentenced.
00:49:30Ramzi And that was chilling.
00:49:33I said, you know, they're never going to give up.
00:49:36They're never going to give up.
00:49:45Richard Eichen My name is Richard Eichen, and I worked on the 90th floor.
00:49:49We used to love standing in the window frame itself and looking down at the Empire State Building.
00:49:56It was almost like being in an airplane.
00:49:57It was really, really pretty.
00:49:58I remember seeing one time
00:50:02There was a rainbow, but that was below us
00:50:04So I've never looked down at a rainbow before
00:50:06The morning of 9-11
00:50:08It was an absolutely beautiful day
00:50:10I went upstairs, 90th floor
00:50:13I remember leaning against the wall
00:50:14Reading the New York Times
00:50:16Holding a bagel in my hand, holding the Times against the wall
00:50:18And all of a sudden
00:50:20I heard the
00:50:22The loudest sound I've ever heard
00:50:24Walls went in
00:50:27Doors opened, flames came out
00:50:29I was just in the fires of hell
00:50:31The wall in front of me
00:50:32Looked like bubbles, it almost looked like it was alive
00:50:35Bubbling flame coming towards me
00:50:37I remember going like this
00:50:38As the flames were coming towards me from that wall up the corridor
00:50:41And that's when I looked down and saw that my shirt was full of blood
00:50:44I let out three
00:50:47End of life screams
00:50:57All I remember is all this glass just blew out behind me
00:51:06Then I remember looking out the window and I saw like briefcase
00:51:10I saw a chair
00:51:11I saw a person in a chair
00:51:14I stood there
00:51:15I stood there in shock
00:51:17Awful lot of smoke from one of the towers of the World Trade Center just occurred
00:51:22This just in, you were looking at obviously a very disturbing live shot there
00:51:27That is the World Trade Center and we have reports that a plane has crashed into one of the towers
00:51:329-11 will test not only America's resolve
00:51:35But every aspect of the World Trade Center's innovative design
00:51:39Its steel supporting walls
00:51:42Its rigid tube structure
00:51:44Stairwells
00:51:46And lightweight floors
00:51:47All are now subject to a brutal assault
00:51:50The first airplane hit the North Tower
00:51:57At about 8.46 a.m
00:52:0010,000 gallons of fuel loaded with passengers
00:52:04And it's traveling at 500 miles an hour
00:52:07The brunt of the force went into floors 94 to 98
00:52:14A number of exterior columns were completely severed
00:52:18A number of core columns in the middle were severed
00:52:21Many people saw that huge fireball
00:52:25That accounts for about a third of the fuel that was in the airplane
00:52:31The second third of the fuel just distributed across impact floors
00:52:37The World Trade Center's main selling point
00:52:40An acre of open office space per floor
00:52:43Now contributes to the disaster
00:52:45All that open space with no intermediate columns
00:52:49Nothing in your way
00:52:51It's kind of like an arsonist's accelerant
00:52:53It starts setting a lot of other stuff on fire
00:52:56Many of the towers nearly 200 elevators
00:53:00So groundbreaking when designed
00:53:02Are now a conduit for flames
00:53:04The last third of the fuel just went down the core
00:53:10Down the elevator shafts
00:53:12When elevator doors opened on the ground floor
00:53:16There was fire jetting out some of those elevator doors
00:53:21That morning I was in the elevator on my way to 67th floor
00:53:29And a tremendous shock threw us against the wall
00:53:34And then the car started to fall
00:53:40It came to an abrupt stop
00:53:42We had probably fell about 15 floors
00:53:45The smoke started to build
00:53:46We could hear debris falling on the top of the car
00:53:50And none of us were sure the car was actually going to stay where it was
00:53:54Myself and another gentleman pried the doors open
00:53:57We were in the express portion of the elevator shaft
00:54:00And therefore there were no openings above or below
00:54:02No way to get our way out
00:54:05The very design innovation that allows the buildings to rise so high
00:54:08Express elevators with limited exits
00:54:11Now leaves the passengers with no obvious means of escape
00:54:14There were five other men in the elevator
00:54:16The only person that I knew was Jan, the window washer
00:54:19Because he did the interior windows on our floor
00:54:23Jan Damcher carries with him a tool of his trade
00:54:26That makes all the difference
00:54:28Jan reached into his bucket
00:54:30And pulled out the blade to the squeegee that he had
00:54:33And we just began to peck at the wall
00:54:36To try and make our way through
00:54:38The three stairwells, purposely clustered in the middle as part of the open floor plan
00:54:44Are instantly destroyed
00:54:46Trapping more than 1,300 people above the impact zone
00:54:49Anyone at or above impact in the north tower
00:54:53Because of the stairwell design, your fate was sealed
00:54:56Because all of the stairwells were severed and impassable
00:54:59Somebody in a nearby building
00:55:02You can see a big white sheet being waved out of a broken window
00:55:06One of the linens used to cover the tables at windows on the world
00:55:09They were trying to let us know that they're still up there
00:55:13To come get them
00:55:15When the first plane came in and hit the north tower
00:55:20First, the three exit stairwells were so close together
00:55:25All three were cut off at once
00:55:28And then second, it cut off the only standpipe for water for the sprinklers
00:55:33That meant the sprinklers in the building did not work anywhere
00:55:37The sprinklers were installed after a fire in the 1970s
00:55:41But the system lacks redundancy
00:55:43And was never designed for a blaze of this intensity
00:55:46Because the fire sprinkler system had been completely incapacitated
00:55:50And an inferno was burning inside of the towers
00:55:53All of these factors come together to create a fire that was out of control
00:55:56And there was no way it could be stopped
00:55:58Police helicopters tried to approach
00:56:01But there was no realistic means of evacuation
00:56:07I saw some of the guys make an unthinkable decision
00:56:15I saw them exit the building at the 105th floor level
00:56:21And I'll never forget seeing those guys
00:56:27In a free fall
00:56:31It's 9.02 a.m. in the south tower
00:56:37I came nose to nose with a fellow named Bobby Call
00:56:42And I said, Bobby, what have you heard? What do you know?
00:56:44And in the midst of him telling me that
00:56:46Just this big roar in the sky
00:56:49I just happened to raise my head and I saw
00:56:51That caught my attention was a plane
00:56:53Like this plane, you're actually coming towards me
00:56:54It sounds as if you're in the plane
00:56:56The plane is about to take off
00:56:58That revving sound
00:57:00And I dove under the desk
00:57:02I'm gonna die
00:57:09Another plane just hit
00:57:11Right
00:57:12Oh my God
00:57:13Another plane has just hit
00:57:14It hit another building
00:57:16Flew right into the middle of it
00:57:18Second jet
00:57:20Come crashing into the second tower
00:57:22What is going on?
00:57:24With both towers now impacted by hijacked airliners
00:57:30A deadly calculation begins
00:57:33How soon can they be evacuated?
00:57:35And with their one-of-a-kind engineering
00:57:38How long can they stand?
00:57:45Planes have crashed into each of the towers of the World Trade Center
00:57:51Just within the last few minutes
00:57:54It's 9.03 a.m. on September 11, 2001
00:57:57Both towers of the World Trade Center are now on fire
00:58:03The south tower was hit by the second plane
00:58:06I was standing on the 84th floor
00:58:09My mind said, this building's going over
00:58:12Our building swayed way to the west
00:58:15With loud creaking of steel and so on
00:58:17It came back to vertical
00:58:19The buildings initially stand
00:58:21Thanks in part to the rigid steel tube structure
00:58:25It was something that you can trace back to the wind resistance
00:58:29That was built into the World Trade Center
00:58:31That allowed one wounded part of the tower
00:58:34To be compensated for
00:58:36So that instead of this face falling down
00:58:38It was actually being held up over here
00:58:40In the north tower
00:58:42For those below the impact zone
00:58:44And the severed staircases
00:58:46Evacuation begins
00:58:48And so all I knew is on three sides of me I had flame
00:58:53But I knew that something had to happen
00:58:55That I needed to get out of there
00:58:57But for six passengers trapped in an express elevator between floors
00:59:01Their sole hope is to pry their way out
00:59:04Using the only tool they have
00:59:06Window washer Jan Dampcher's squeegee
00:59:09I was in the elevator at the 50th floor
00:59:12Taking small chunks out of the wall at a time
00:59:14To try and make our way through
00:59:16One of our party dropped the blade and fell through the crack
00:59:19Our hearts sank
00:59:21Jan reached into his bucket again without a word
00:59:22And pulled out the handle to the squeegee
00:59:24And we used that brass handle to score a large X in the wall
00:59:27And then begin to kick out sections until we were able to break through
00:59:32Into what was a restroom on the other side
00:59:35We got into a stairwell and started to make our exit
00:59:38In the south tower
00:59:40Though he doesn't realize it
00:59:41Brian Clark faces a life or death decision
00:59:44Head for the stairs, let's go
00:59:46Ahead of me was stairway B
00:59:48And to my left was stairway A
00:59:50The impact of the airplane onto the south tower
00:59:56Severed two of the stairwells
00:59:59But spared one
01:00:01Only one stairwell was still passable
01:00:03And people had a hard time finding it
01:00:05There were 619 people in the south tower
01:00:08At or above impact who died
01:00:10I had the sensation of being pushed to the left
01:00:14And I went with it to stairway A
01:00:17Brian Clark manages to locate the south tower's
01:00:20One remaining stairwell
01:00:22In the north tower
01:00:24All three of the centrally located stairwells
01:00:26Have been destroyed
01:00:27And down we started
01:00:29I heard this banging noise inside the 81st floor
01:00:32And this muffled voice saying
01:00:34Help, help, is anybody there?
01:00:36I can't breathe
01:00:37And my flashlight caught this hand waving in the air
01:00:41And lifted him up
01:00:43And we fell onto a pile of debris
01:00:45With this stranger on top of me
01:00:48And he gave me this great big kiss
01:00:50And I dusted myself up
01:00:52And we stood up
01:00:53And I put my hand out
01:00:54And I said
01:00:55I'm Brian Clark
01:00:56And I said
01:00:57Stanley Brayman
01:00:58He says
01:00:59We'll be brothers for life
01:01:01He said
01:01:02All my life
01:01:03I always wanted a brother
01:01:07And I find that person today
01:01:09And this good old Irish man
01:01:11Put his hand around my shoulder
01:01:12And says
01:01:13He says
01:01:14Come on buddy
01:01:15Let's go home
01:01:16In 1993
01:01:18Evacuation took up to 12 hours
01:01:20In dark, smoky stairwells
01:01:22But improvements afterwards
01:01:24Including enhanced lighting
01:01:26Means that on 9-11
01:01:28Evacuation is remarkably successful
01:01:30What happens below impact
01:01:33Is really a story of a miraculous evacuation
01:01:36In which 99% of the people below the floors of impact
01:01:40Managed to get out of the towers and live
01:01:42Almost everyone below impact gets out
01:01:45We got on the stairwell
01:01:46And once we were inside
01:01:47There was fluorescent lighting
01:01:49The air was clean
01:01:50I never saw any smoke in there at all
01:01:52And at that point
01:01:54We just ran
01:01:55We just ran
01:01:58As that happens
01:01:59With the fireproofing gone
01:02:01Temperature in that steel begins to rise very quickly
01:02:04And those floor trusses start to sag
01:02:07An inferno was burning inside the towers
01:02:09With what was left of the 10,000 gallons of fuel
01:02:12At this point the clock is ticking
01:02:14We finally made it to the lobby
01:02:18We're looking at this ashen gray site
01:02:21We ran out of that building
01:02:23Jumping over all sorts of debris
01:02:26Brian Clark and Stanley Premnaf
01:02:29Are two of just 18 people above the impact zone
01:02:32Who find that one path to survival
01:02:35They look up in time to see the steel columns
01:02:38In the south tower bend inward
01:02:40The core columns are just going like this
01:02:43And they're starting to rip the floors away from the exterior columns
01:02:47Once the floors were gone
01:02:48There was nothing connecting the core and the exterior
01:02:51And then the whole building is going to collapse
01:02:54We're watching this building
01:02:55And I'm telling him
01:02:56It's going down now
01:02:58I said there's no way
01:02:59That's a steel structure
01:03:00And in the middle of that sentence
01:03:02You'll really see it tilt over like this
01:03:14As it comes down
01:03:16Before it disappears into the smoke
01:03:20What's happening to the tower's steel
01:03:22Won't be fully understood for years to come
01:03:24But it's clear to onlookers
01:03:26Structural failure is imminent
01:03:30Now raining debris on all of us
01:03:32We better get out of the way
01:03:37Once I heard that roar and I turned around
01:03:39And I saw it was the building coming down
01:03:41I just ran, ran, ran, ran, ran
01:03:50You couldn't see three or four yards ahead of you
01:03:53It looked like a moonscape
01:03:56Suddenly I realized I can't breathe
01:03:58And so I go like this
01:03:59And I see that my mouth is full
01:04:01Just full of the stuff
01:04:03And so I took two fingers
01:04:04And I dug the stuff out of my mouth
01:04:06So I could breathe again
01:04:09And somebody yells out
01:04:11Watch out
01:04:12I see the top of one
01:04:14Starting to come unstable
01:04:15As the north tower comes down
01:04:17The first thing you see
01:04:18Is that top part begin to topple
01:04:20Like a tree kind of toppling over
01:04:22Just sort of falls straight down
01:04:23And crushes everything below it
01:04:3129 minutes after the south tower collapses
01:04:36The north tower falls
01:04:40The World Trade Center vanishes
01:04:43Replaced by a cloud of dust
01:04:47Both towers
01:04:48Took 10 years to build
01:04:50And 10 seconds to collapse
01:04:53For those, like Charles Makish
01:04:55Who helped build them
01:04:56And build the life here
01:04:59Losing the towers is almost impossible
01:05:01To believe
01:05:04Am I dreaming?
01:05:06Am I gonna wake up from this?
01:05:08And I'm trying to digest
01:05:11What I had just seen
01:05:13I just, you know
01:05:15Sometimes you don't believe your own eyes
01:05:18It was just unthinkable
01:05:20That they would collapse
01:05:24What just happened?
01:05:29The towers are gone
01:05:32But new disasters are looming
01:05:34There was a real concern
01:05:36About the slurry wall collapsing
01:05:38And you flood the subways
01:05:39And you flood lower Manhattan
01:05:41And the investigation begins
01:05:43With a fundamental question
01:05:45Was there something wrong
01:05:46About the way that they built those towers
01:05:48That made them prone to collapse?
01:05:50The world comes to know it as ground zero
01:05:55The world comes to know it as ground zero
01:05:58But to those on site
01:06:00The wreckage of the World Trade Center
01:06:02Is simply called
01:06:04The pile
01:06:08The ash on the ground was like it snowed four inches
01:06:10You could actually sit there and count the floors
01:06:15It was like rock strata in the Grand Canyon
01:06:18You know, floor by floor
01:06:20Just ash
01:06:22As a result of the compression and the heat
01:06:25There was nothing left that was in those towers
01:06:27These intense compacted areas of debris were burning and they're superheated
01:06:37And anything that could burn and melt inside of it was
01:06:41That site was the most dangerous site I ever worked on in my whole career
01:06:46There was unstable piles of buildings hanging over fires burning
01:06:50Equipment moving around
01:06:52People were scrambling to find people
01:06:53And there was a thought that you would find people alive
01:06:56As engineers sift through the wreckage searching for survivors
01:07:00Only a few people realize that there's a threat of more disasters to come
01:07:05So we were very concerned that they would hit a weak spot and actually fall down and get killed
01:07:13One of the equipment operators left this big excavator because he had to go get something
01:07:18He thought he was on solid ground
01:07:20And when he came back he couldn't find his excavator
01:07:22It had disappeared
01:07:24It fell three floors down in the basement of the World Trade Center
01:07:27The World Trade Center's incredible cooling system
01:07:30Relying on thousands of gallons of Hudson River water pumped into the towers
01:07:35Was an engineering marvel when it was built
01:07:38Now the maze of pipes represents a life-threatening danger
01:07:41When the buildings collapsed there was a concern that maybe water from the Hudson River
01:07:46Could get into the site through those pipes
01:07:49The valves were buried and no one knew where they were
01:07:52You couldn't see them
01:07:54But in the first couple of days Port Authority personnel went over and closed those valves
01:07:57They closed them by hand
01:08:00And there's fear another of the World Trade Center's innovations is on the brink of disaster
01:08:05The slurry wall
01:08:07So carefully constructed to keep river water from flowing into the complex's foundation
01:08:12One breach of the sides of the bathtub would cause catastrophic flooding
01:08:17When the towers collapsed they also destroyed all the floor system that used to support the slurry wall
01:08:23And that was a vast labyrinth of floors and spaces that were 75 feet deep and covered 10 acres of the site
01:08:31So there was a real concern about the slurry wall collapsing and the basement filling up with water
01:08:38Underneath here, underneath the subway
01:08:41If you were to move a crane in the wrong place and then suddenly the bathtub or the slurry wall collapses
01:08:46You open up a gateway to the Hudson River and you flood the subways and you flood lower Manhattan
01:08:52It would have been a catastrophe
01:08:54It was a real concern that that could happen because we couldn't ascertain the condition of the slurry wall
01:09:00Engineers devise a plan to avert disaster
01:09:05So the best solution to that was to actually plug up the entire lower Manhattan tunnel system
01:09:12So that if something catastrophic happened that the water would stay in the tunnel and not flood the entire system
01:09:18And so it was a race against time
01:09:21But ultimately, the slurry wall holds
01:09:25This cornerstone of the original vision survives another assault
01:09:29The slurry wall survived a bombing and the crash of the planes and the collapse of the towers
01:09:35If anything is an eighth wonder of the world, it's the slurry wall
01:09:39When the original Trade Center was built, there was a bank vault built for the Swiss bank
01:09:44In 2001, that bank vault was being used by the Bank of Nova Scotia
01:09:48And they had gold, bullion and silver there
01:09:50And it was deep down in the World Trade Center
01:09:52After the buildings collapsed, obviously the banks wanted to get to that gold and silver bullion that they had
01:09:58In today's dollars, there was probably three to four billion dollars worth of gold and silver there
01:10:03So we knew where the vault was, but the doors on the vault were operated electrically
01:10:07And you couldn't get down to the vault except through an elevator
01:10:09Now they were intact, but there was no power on the site
01:10:11So us engineers were able to figure out a way of getting power to the site
01:10:16And they were able to get and remove the gold bullion, open the doors and truck it out
01:10:20It took, I think, almost 120 armored trucks around the clock for several days to move all that gold and silver out of the site
01:10:28It was one of those crazy things that just happens in the midst of all this terror and everything
01:10:33And destruction
01:10:34While work at the pile goes on, what began as a rescue is now a recovery, pausing to honor each victim
01:10:44I remember every time they would find a dead body, there was a horn that they would blow
01:10:49And I would say, oh, I would make the sign of the cross and say, oh, they found somebody
01:10:52There were 70 Port Authority staff that I knew
01:10:57And another 70 other people associated with the Trade Center that I knew
01:11:03That perished
01:11:05We attended about a hundred memorial services for about a period of four to five months
01:11:10Among the dead, Rocco Camage, who had to be strapped in outside the World Trade Center to wash their wider upper windows by hand
01:11:21On 9-11, Camage was trapped, along with 200 others, on the 105th floor of the North Tower
01:11:28And Port Authority architect Frank DiMartini, who predicted the World Trade Center could withstand the impact of a 707 jetliner
01:11:36I believe the building probably could sustain multiple impacts of jetliners
01:11:43But could not foresee a 767 loaded with fuel
01:11:47On 9-11, I got a call from Frank DiMartini
01:11:52He was on the phone, he's frantic, absolutely frantic
01:11:55He was located probably two or three floors below the airplane impact
01:12:01And he didn't know what happened, he didn't know it was an airplane
01:12:06He knew those buildings inside out
01:12:09He could have easily taken an elevator or stairway down and escaped
01:12:14Instead, he stayed behind to direct other people on how best to exit the building
01:12:20And that cost him his life
01:12:22He's a hero, an American hero
01:12:24The pile smolders for over three months
01:12:30But the investigation into exactly why and how the towers fell is just beginning
01:12:35Among the first questions, did the precision-designed steel beams and floor trusses have a deadly design flaw?
01:12:42There was a lot of concern that the steel might have been built to the wrong specifications
01:12:47You had what used to be a straight piece of steel
01:12:51Completely bent in a curl, ripped apart
01:12:55It's shocking
01:12:56On 9-11, I got into the newsroom, an editor tapped me on the shoulder
01:13:11I said, at 6 o'clock, you will file a story on why the towers fell the way they did
01:13:18And that is how I began on the World Trade Center's story
01:13:24For engineers, investigators, journalists, and victims' families
01:13:29It's urgent to understand what caused the World Trade Center to collapse
01:13:33And in order to understand who lived and who died, you need to be able to answer the question as to why did they stand and why did they fall
01:13:39But more importantly, was there something fundamentally wrong about the way that they built those towers that made them prone to collapse?
01:13:45200,000 tons of steel were used to build the Twin Towers
01:13:51Engineers soon realized that one key to understanding what happened
01:13:55Lies in the twisted remains at Ground Zero
01:13:58There was a lot of concern
01:14:00A, that the steel might have been built to the wrong specifications
01:14:03And B, that there might have been a structural flaw in the design of the towers
01:14:07The first week of October, we were allowed to go and start collecting steel from the towers
01:14:13It was overwhelming
01:14:16Firefighters, they were still doing recovery
01:14:19They're on their knees with buckets and picks looking to identify remains that were left in the debris
01:14:24And at the same time, these engineers are pulling up pieces of steel
01:14:28Somehow, in this huge jigsaw puzzle of debris, they had to find just the parts where the most critical things happen
01:14:35But if the steel holds a clue to their destruction, there is a problem
01:14:40Mayor Rudolph Giuliani wants to get everything out of there as quickly as possible
01:14:44Just move it out, move it out, because he wants to get New York City back
01:14:47There were a lot of problems with the engineers trying to get steel samples from the site
01:14:54So they could study them was almost impossible
01:14:57There was stuff that the investigators hadn't even had a chance to look at
01:15:00So they end up going to the scrapyard to try to find steel to see if this is steel that they really needed
01:15:04When we first got to the steel yards, we were just dazed at what we were seeing
01:15:11You had what used to be a straight piece of steel, completely bent in a curl, ripped apart
01:15:19It's shocking, we just started working to get through a pile of steel as quickly as possible
01:15:26Engineers will spend years analyzing thousands of pieces of evidence, some of which are downright shocking
01:15:32I went up to one of the steel pieces, it had a coating on it that you could just wipe away with your bare hand
01:15:40That was the fireproof coating that they put on the steel
01:15:44It was surprising to me to see how easily that it came off
01:15:49Fireproofing has been an issue ever since a mob-connected contractor hired to do the job was found to be taking shortcuts
01:15:56Now, the loss of the fireproofing is one of the first puzzles engineers worked to solve
01:16:02The reason why they lost their fireproofing
01:16:07We have two airplanes ramming into the towers
01:16:12You now have a debris field of metal traveling through the space
01:16:18All this debris going through removed the fire insulation from the columns
01:16:25So now you had bare steel exposed where it used to be protected
01:16:30The fate of those towers was sealed as soon as the planes hit them
01:16:35And the fireproofing had been stripped from the core columns
01:16:38The other aspect of fire safety was sprinklers
01:16:43The water mains severed with the aircraft impact
01:16:47There was only one pipe in the building that was carrying water for the sprinklers
01:16:52And that speaks to the lack of redundancy that they had for the system
01:16:56So, right away, you lost your two main systems for fighting fires
01:17:01Your sprinklers and your fire insulation to protect your steel
01:17:04And the fact that the buildings had open spaces in the floor plan
01:17:10This would allow the flames to spread faster
01:17:13All of these factors come together and lead to extreme temperatures
01:17:17Well beyond what the towers can withstand
01:17:20It was estimated that the temperatures reached a thousand degrees
01:17:27Investigators focus on another clue
01:17:29How the planes impact on the towers critical steel supporting columns
01:17:34Sets off a catastrophic chain of events
01:17:36When steel is that hot, it's not like steel, it's like licorice
01:17:41It's very soft
01:17:43And you can see the face of the tower bowing inward
01:17:46As the time for collapse begins to get closer
01:17:49But in the inferno of 9-11, there is one unanticipated success
01:17:53A truss system on top of each tower called the hat truss
01:17:59Originally installed to support giant TV antennas
01:18:02The hat truss is a grillage of steel
01:18:06Connecting the perimeter wall to the internal core towers
01:18:11But on 9-11, the hat truss played a role
01:18:15That they were never designed for
01:18:18It allowed for loads to redistribute from columns that had been severed
01:18:25Onto other columns that were still intact
01:18:29Spontaneously, the building kind of keeps itself from falling
01:18:34Because all the loads that could no longer go on the severed columns
01:18:38Were transferred out to the side
01:18:40The hat trusses keep the tower standing long enough for thousands to evacuate
01:18:44But ultimately, the assault and the resulting heat are overwhelming
01:18:50At some point, not enough columns are left
01:18:54And the hat truss cannot redistribute all of the loads from the inside to the outside
01:19:01The core columns have been stripped of fireproofing and weakened
01:19:05And so, they bent inward
01:19:07Once you bend those columns, they can't hold really anything
01:19:10The columns begin to be pulled inward by the floors
01:19:16And so, what happens is the top part of the building bears down on those bowed columns
01:19:24The violence of the top of the building coming down ends up crushing everything below it
01:19:29Gravity takes over and you get a pancaking event bringing the entire tower down
01:19:35And there's a catastrophic collapse
01:19:41That collapse is about 2.5 on the Richter scale
01:19:50The fact that it fell straight down led to conspiracy theories
01:19:55Because that's the same way if you have a planned demolition that a building would collapse
01:20:05It almost looked like they disappeared
01:20:08Yes, the twin towers were built of glass, steel and aluminum
01:20:13But, they were mostly air
01:20:16It's almost like you can think of a balloon
01:20:18If you puncture a balloon, what's left? Not much
01:20:22Because most of that balloon was air
01:20:25Could the towers have been engineered to be more resilient?
01:20:29Could safety systems have been improved?
01:20:32Chief Engineer Leslie Robertson, who oversaw every aspect of the tower's design and construction
01:20:39Agonizes over what might have been
01:20:41Les Robertson was very saddened
01:20:44He felt that maybe there was something he could have done from a structural engineering point of view
01:20:49That would have made a difference
01:20:51And I asked him what that was and he said, I don't know
01:20:54He said, but I just feel like, you know, I designed the buildings, they should have stood
01:20:57I think it is underestimating the violence of the attack
01:21:09To think any changes in the design realistically would have altered the outcome
01:21:18More fireproofing, more sprinklers, any improvement
01:21:23I don't think any of that would have mattered
01:21:26The attack was just too overwhelming
01:21:28How could this have been prevented?
01:21:30Don't allow any kamikaze airplanes to strike your building
01:21:34The length of time that the building stood, which is a testament to the engineering that was put into them
01:21:42Was the biggest factor in saving lives that day
01:21:45Because it allowed so many people, virtually all the people below the impact zones, to get out
01:21:50That is something that we should never forget
01:21:55Engineers and architects face one final test
01:22:00What could replace the World Trade Center complex?
01:22:03And how to make it safe?
01:22:05For more than a decade after 9-11, there's a hole in New York City's skyline
01:22:12After the attacks of 9-11, there was a lot of soul searching
01:22:16What should be done to replace the Twin Towers?
01:22:20And there were many controversial different plans
01:22:24And indeed, what was finally decided was to build a single, very tall tower
01:22:31The State of New York holds a design contest, and a winner is announced
01:22:36Dubbed the Freedom Tower, the unusual design features an off-center spire
01:22:40That echoes the Statue of Liberty's arm and torch
01:22:44But it will never be built
01:22:46A decision no longer made solely by the Port Authority
01:22:49Just prior to the attacks and collapse of the World Trade Center
01:22:52The Port Authority had signed over a lease to Silverstein Properties
01:22:56Larry Silverstein becomes essentially the landlord
01:22:59So that means that he has the right to play a part in deciding what's going to happen at the World Trade Center site
01:23:05A new, more practical design takes shape
01:23:08The new building bears little resemblance to the original design
01:23:11Except for the height
01:23:13A symbolic 1776 feet tall
01:23:18Construction begins
01:23:20Until one city agency that does have a say
01:23:23The New York City Police Department slams the brakes
01:23:26There was a concern about the location of the building in terms of how close it was to streets
01:23:32And the possibility of the threat of car or truck bombs
01:23:36And the end result is that they essentially built the building around a concrete pedestal
01:23:43That protected it from any type of an attempt to attack it from the ground
01:23:47When the tower, now simply called One World Trade Center, opens in 2014
01:23:53Tenants are told the building is far safer than its predecessors in every way
01:23:58The new building is built in a more conventional way
01:24:02It does not have the steel tube structure
01:24:04It's got redundant sprinkler systems
01:24:06One of the major changes was the stairwells
01:24:09They're wider, they're pressurized so that you can keep out smoke and flame
01:24:16And also the walls are reinforced so that they won't collapse so readily
01:24:22And in addition, there's now a dedicated stairwell for first responders
01:24:26To be able to get up while a building is being evacuated
01:24:28Perhaps more impressive than the tower itself
01:24:36Is the memorial built to commemorate the old buildings
01:24:40And honor the victims of 9-11
01:24:43You have the new One World Trade Center
01:24:46But you preserve the site of the original footprint of the Twin Towers
01:24:51With their reflecting pools and the memorial with the names
01:24:55It signifies the loss or the absence
01:25:00And it also signifies, you know, the continuation of life
01:25:06People were determined to rebuild that area
01:25:10And honor the people who died
01:25:12And create that beautiful memorial down there
01:25:17And I think that's a perfect reflection of the resilience of New Yorkers
01:25:22We're gonna make this area once again a golden place
01:25:2720 years later
01:25:32For those who survived the fall of these iconic buildings
01:25:359-11 is something they still carry every day
01:25:38It's a fairly painful memory
01:25:42And even till today
01:25:45A lot of those memories are very fresh in my mind
01:25:48Some of the sights, sensations
01:25:51The feelings
01:25:53A sense of loss, grieving
01:25:55I used to just sit there
01:25:57And just cry
01:25:59Why did this have to happen?
01:26:01And then, you know, I'm not the only one
01:26:05Who knows what's gonna happen tomorrow?
01:26:08Instead of dwelling on those things that are unanswerable in the past
01:26:11It really leaves you and it leaves me for certain
01:26:15In the present
01:26:17That's where I spend most of my time
01:26:20In the four floors that we had
01:26:23Nobody else survived but me
01:26:26I don't understand how I was spared
01:26:29I don't know
01:26:31But I was the only one who walked away
01:26:33Life is very, very random
01:26:36One day you show up at work, buy a bagel
01:26:38You think it's gonna be just another day
01:26:40Looking out the window and everything changes
01:26:42And a lot of other people didn't even go home that day
01:26:44It just shows the randomness and fragility of life
01:26:48And for those whose vision created the World Trade Center
01:26:54This remains an ending impossible to conceive
01:26:58We asked David Rockefeller, along with Les Robertson
01:27:03And Guy Tazzoli
01:27:05Would they come down to the shattered remains
01:27:08Of Ground Zero and stand there for a portrait
01:27:16I watched them as they stood down there in the ruined remains
01:27:21Of the Trade Center at Ground Zero
01:27:22Thinking about what they'd created and what they'd lost
01:27:28Just like the rest of us
01:27:31The Twin Towers touched their hearts in a different way
01:27:35Because they were the builders
01:27:38They were the makers
01:27:41They were the movers
01:27:43The city did heal
01:27:47Having taken the worst of it
01:27:49And then rising out of it
01:27:53By rebuilding
01:27:55By remembering
01:27:57That's the tragedy and the triumph
01:28:02I think
01:28:04That looking back 20 years allows you to understand
01:28:09Those are the things that
01:28:11We use and we need to look back on
01:28:13And that is something that we should never forget
01:28:19That is something that we should never forget
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