NARRATOR: An icon rises in the New York City skyline:
One World Trade Center.
104 stories tall,
reaching a symbolic 1,776 feet.
It's been an epic journey filled with troubling problems
and innovative solutions.
We're really at the cutting edge on everything at this site.
T.J. GOTTESDIENER: This building is not a skyscraper.
It's taller than a skyscraper.
This is in another league.
NARRATOR: For architect David Childs, it's the challenge of a lifetime.
We knew this building would have all eyes on it
and it needed new technical advances that would set the path
for other buildings in the future.
NARRATOR: Next door is the 9/11 Memorial, to honor those who died
in the worst terrorist attack in American history.
LOU MENDES: Future generations need to understand
what took place at this site.
NARRATOR: And 70 feet belowground is the 9/11 Museum.
PAULA BERRY: The role that this museum plays is really to punctuate
what that day means for you.
NARRATOR: After more than a decade,
the building of One World Trade Center is almost complete.
CHILDS: It is very important that we did rebuild.
It gave us a chance to rebuild better.
JOE DANIELS: We have the DNA of strivers--
that's part of the American character--
and so there was this desire to rebuild tall again.
NARRATOR: It's the birth of an icon.
But will it live up to its promise
to be beautiful, safe and ahead of its time?
"Ground Zero Supertower," next on NOVA.
ANNOUNCER: Major funding for NOVA is provided by the following:
Supporting NOVA and promoting public understanding of science.
And the Corporation for Public Broadcasting.
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NARRATOR: A beacon rises 104 stories
up to the top of the tallest building in New York--
perhaps the tallest building in the Western Hemisphere.
PAUL GOLDBERGER: Going back into the sky is really important,
because that's something that was taken away.
And I think it's appropriate to put it back
to show that the life of the city goes on
and is more powerful than the forces that attacked it.
NARRATOR: Its creators' hopes and dreams are riding on it
being not only the highest, but the safest,
most innovative and beautiful skyscraper in America.
CHILDS: I feel a great sense of accomplishment;
this building is a strong visual image
of our resilience, coming back after this terrible tragedy.
NARRATOR: The tragedy was the worst terrorist attack
in American history, September 11, 2001,
causing unimaginable destruction,
killing almost 3,000 people.
Out of the ashes, one of the world's
most innovative skyscrapers is rising.
Soon, its beacon will illuminate the New York City skyline.
JOHN GEBBIE: You're going to look up there
and you're going to identify with 9/11,
with One World Trade Center
as a result of this beacon of light.
GOTTESDIENER: I know for me, wherever I am and I can see that light,
I'll know that as Americans, as architects, as New Yorkers
that we have resiliency.
We've triumphed.
We've come back.
We've built this.
We're reaching for the stars.
NARRATOR: It has taken over a decade to lift this beacon
a symbolic 1,776 feet to the top of One World Trade Center.
But it is just one of the many challenges
architects and engineers have faced
on this 16-acre construction site known as Ground Zero.
Today, it is bustling with activity
from hundreds of feet in the air
to seven stories below the ground.
BILL BARONI: 12 years ago, people thought nothing would ever happen here.
Four years ago, people'd think nothing was happening here.
And now people know this site is back.
NARRATOR: When complete, the site will include
a train station to rival Grand Central,
six new towers,
and at its heart, the 9/11 Museum and Memorial,
built in the footprints
of the Twin Towers of the World Trade Center
that once stood here and were destroyed in the attack.
We owe it to those that didn't get to come home,
who didn't coach another Little League game,
didn't get to see their kid get married.
That's why we're doing it.
NARRATOR: And so as the Port Authority of New York and New Jersey
build this supertower, safety is paramount
and a new approach is required.
Back in their day,
the Twin Towers were considered state of the art.
They employed a unique steel structure
that allowed for wide open floor spaces
where up to 40,000 people went to work each day.
But decades later, these marvels of engineering proved vulnerable
in a way no one had foreseen.
Architect David Childs watched the events of 9/11 unfold
from his office in downtown Manhattan,
where at 8:46 a.m., the North Tower was struck by an airplane.
Then the South Tower is hit.
Both buildings are in flames.
CHILDS: I remember walking up to a window
and a young man turned to me with tears coming down his face,
and he said, "Will they fall down?"
And I said, "No," right away,
because I knew that if they hadn't been knocked over,
they wouldn't fall down.
The fire would be put out.
Never has a steel structure building
in the history of steel structured buildings
ever fallen down for reasons of fire.
NARRATOR: Never before had a steel structure under fire
absorbed the loss of such massive columns from an impact.
At 1,800 degrees Fahrenheit,
it's hot enough to weaken the steel structure.
The North Tower stands for an hour and 42 minutes,
the South Tower for only 56.
Finally, the steel gives way to the heat.
The floors start to sag.
The perimeter steel columns buckle.
The Twin Towers do the unthinkable:
they collapse.
Nearly 3,000 people die.
Several months after the attack, David Childs starts to think
about designing a new tower at Ground Zero.
It is the challenge of a lifetime
to come up with a building strong enough and safe enough
to be built on this site.
Safety has always been a measure of how buildings are built.
Go to Florence.
Some of the great buildings of Florence are all about defense.
Great pieces of rusticated stone,
of metal bars across the windows,
and yet you look at those buildings
and you think proportion and texture and shade
and all the interaction of the different materials.
You don't think about safety today.
NARRATOR: Childs hopes to achieve the same balance through innovation.
CHILDS: We needed to investigate and invent new ways
to show how buildings could be built in the future.
So this building must look forward
in terms of new technology, new inventions.
How do we make the ideal building of the future
look forward?
NARRATOR: As he looks for ways to answer this question,
Ground Zero is in ruins.
Rescue workers are desperately searching through the rubble
for the remains of those who were still unaccounted for
when beneath more than a million tons of debris,
engineers discover another disaster waiting to happen:
the site is at risk of being inundated by the Hudson River,
only a few hundred feet away.
GOTTESDIENER: Many people aren't aware
that this site at one point was underwater.
It's landfill.
Over time, docks and wharves and landfill
slowly increased the tip of Lower Manhattan.
What this means is that the site that was occupied
by the World Trade Center is literally in water.
NARRATOR: To build the world's tallest towers on land like this,
engineers had to find a way to keep the river out.
They came up with an ingenious idea.
This entire complex was built
inside what we call a "slurry wall."
NARRATOR: The slurry wall encircled the World Trade Center complex
like an enormous bathtub.
A bathtub where the World Trade Center site was built within.
It essentially kept out the Hudson River.
It kept out all the wet soil surrounding the site.
NARRATOR: The slurry wall was made up of over 100 panels,
each one 22 feet wide and seven stories deep,
going all the way down two feet below bedrock.
Each section was excavated and filled
with a gluey clay mixture called slurry,
which keeps silty soil and water from getting in.
Next, a 70-foot-long steel frame weighing 22 tons
was lowered into the slurry-filled panel.
Concrete was slowly pumped into the panel
and the slurry, which is much lighter,
rose to the surface and was pumped out.
When the concrete hardened,
they repeated the process over and over again,
forming a massive underground wall.
LOU MENDES: Once the wall is built,
they proceed with the installation of tiebacks.
These tiebacks actually hold the wall to the rock.
NARRATOR: Tiebacks are long steel rods
that go all the way down to bedrock to support the wall.
They become diagonal structural elements
that pull the wall to the rock.
GOTTESDIENER: So the whole site is basically a bathtub
pushing back the waters of the Hudson.
NARRATOR: After 9/11, it looked as though this enormous bathtub
might have been weakened and could collapse.
There was real concern that this wall was going to be breached.
WORKER: These walls are coming in.
They moved in around six inches.
These walls hold back the river, so if these walls cave in,
this place is going to get flooded out by the river.
DANIELS: A disaster that was already incalculable
in terms of the human loss
and the loss to just Lower Manhattan and New York City
would have gotten that much worse.
NARRATOR: Securing the slurry wall became a top priority.
Soon, engineers discovered that
the 1.8 million tons of debris filling the bathtub
were actually preventing it from collapsing.
LOU MENDES: The debris was actually acting as a barrier
to keep the wall in place.
That's why we couldn't just remove all the debris;
we have to remove it in lifts, in pieces.
And we did this like a mining operation around the entire pit.
And every elevation of debris we removed,
we had to install new tiebacks.
Once the new tiebacks were installed,
we felt more comfortable that the wall was now
secured properly, was structurally sound.
NARRATOR: A new liner wall was built right in front of the original,
but a section of the old one has been left exposed
as a reminder of what happened here.
DANIELS: The very last piece of steel to be removed from the site,
the last column, was removed on May 30 of 2002,
and it signified the end of the recovery period.
NARRATOR: The recovery period is over, the slurry wall secured,
nearly two million tons of debris removed.
Now the site is empty.
There is a gaping hole in the New York City skyline,
and no one can agree on how to fill it.
GEORGE PATAKI: Everyone had a different idea
and a different vision of what should happen there.
Some important figures didn't want any memorial,
wanted the whole thing redeveloped.
Others said, "You can't develop anything down there;
it all has to be preserved."
So pulling everything together was not an easy task.
It was certainly frustrating as to how long it took,
although remember, Central Park was probably 20 years late
and six times over budget, and nobody remembers that.
The question is where are you, not how you got here.
NARRATOR: David Childs, along with partner T.J. Gottesdiener
and a team of architects and engineers
are in the thick of it,
rethinking strength and safety from the inside out,
starting at the core.
The core of a skyscraper
is a backbone that runs up the center.
It provides structural support and strength.
Childs' design for the core of this supertower
will use one of the strongest,
most fire-resistant materials around: concrete.
But this isn't just any concrete.
This concrete needs to be so strong,
it means going back to the lab to develop it.
CAS BOGNACKI: This is a concrete specimen
that will be used for Tower One at the World Trade Center.
If you could set this cylinder and put a platform on it,
you can accommodate 1,000 Americans
standing on this cylinder.
You know, normal people, 175 pounds in weight,
1,000 people can be supported
by this four-inch diameter cylinder.
NARRATOR: Concrete is made of sand, stone
and binding agents like lime or cement that,
when water is added, hold the mixture together.
But the recipe can be revised by using less water,
replacing it instead with chemicals
that keep the concrete moist without reducing its strength.
Water makes this concrete move in place.
But you can't have too much water
because when you have too much water, the strength goes down.
NARRATOR: The goal: to make concrete that can withstand loads
of up to 14,000 pounds per square inch.
Normal concrete is about 4,000 psi.
Even the Hoover Dam is no more than 7,500.
But strong concrete has its own challenges.
It hardens quickly, so it's a race against time
to get it into place before it sets.
Driver Eric Szemple has only 90 minutes to get the job done.
ERIC SZEMPLE: Concrete is a perishable item.
We have like an hour and a half to get the load off.
NARRATOR: By 2006, this super-strong concrete
makes its way to Ground Zero,
where construction has finally started.
Crews have less than an hour
to pump it through an elaborate system of hoses
where it is poured into a mold
and secured with steel bars called rebar
that give the concrete something to latch on to.
The hope for this reinforced concrete is that
it will withstand unforeseen challenges in the future.
It's strong.
That's why I call it liquid steel.
NARRATOR: When finished, One World Trade Center
will contain almost 500,000 tons of this liquid steel,
much of it in its core,
which has walls up to six feet thick.
CHILDS: The outside of the core,
this whole center spine of the building is out of concrete.
NARRATOR: The cores of the Twin Towers were compromised on 9/11
because they were made of steel wrapped in thin sheetrock.
CHILDS: Where the planes hit,
that sheetrock was not strong enough
to take that punching sheer.
NARRATOR: At the point of impact, the stairs were destroyed,
leaving nearly 2,000 people trapped above with no escape.
That's why it's critical for One World Trade Center
to have a super-strong concrete core
well beyond existing building codes.
Inside, the core protects a total of 73 elevators.
Some can travel 23 miles an hour,
making them the fastest elevators
in the Western Hemisphere.
The core also has staircases that are extra wide
and pressurized to keep smoke out.
CHILDS: When a door is opened,
that pressure goes out, keeping the smoke away from it.
And that's a very effective thing.
Smoke is a real killer.
NARRATOR: One World Trade Center's concrete core
is designed to avoid the tragedy of 9/11,
where two-thirds of the victims died
because they couldn't get out of the building.
And nothing will remind us of that more
than the 9/11 Memorial and Museum being built next door.
The entrance of the museum will be at ground level,
but the heart of it is being built 70 feet below the surface.
The overall museum is about 120,000 square feet.
Except for the entry pavilion, it's underground.
At bedrock, it's about 95,000 square feet.
NARRATOR: Here, parts of the Twin Towers' foundation
are carefully preserved,
like a section of the original slurry wall
and these huge girders that supported the floors above.
These are the original box beams.
These are the original structure that held up the columns
that held up the North Tower at the north face.
I kind of consider them almost like a dinosaur skeleton;
you look at it and you wonder what was.
DANIELS: This museum is an archaeological space
as much as it is a museum.
So when you go to bedrock
and you see the very footprints where the towers sprung to life,
it is sacred bedrock.
These buildings soared more than 1,300 feet into the sky
and defined the New York skyline.
This notion of authenticity of place,
it was super important to us.
VEGA: You're standing on bedrock.
This is as low as the structure of the World Trade Centers were,
so this is pretty magical right now.
It's becoming more of a construction site
and less of a disaster zone.
NARRATOR: The museum will house artifacts
that have been stored for over a decade
in an old hangar at New York's JFK Airport.
Engineers and architects who went through the debris
had the charge of identifying remnant pieces of the buildings
that could help scientists better understand what happened.
They also were looking for things
that might someday help reconstruct the events.
NARRATOR: In twisted steel and broken beams,
the full scale of what happened on 9/11 can be witnessed.
GREENWALD: This material filled an 80,000- square-foot airline hangar.
What was in that hangar
represented less than one percent
of what was at the site, and it filled it to capacity.
So just walking into the hangar,
you had a sense of just... the enormity of what had happened.
NARRATOR: Some of these artifacts are so large,
they are brought on site before the museum is finished
so it can be built around them.
Like these seven-story tridents.
These enormous pieces of steel, which weigh 50 tons each,
formed the distinctive gothic arch motif
at the base of the Twin Towers.
So many tridents survived the attack,
their silhouette has become a symbol of strength.
In 2010, two were brought on site and set in place.
GREENWALD: The two we chose were in fact side by side on the North Tower.
So you have a twin presentation.
They embody a kind of memory
of the twin-ness of the Twin Towers.
NARRATOR: Over the next few years,
the entrance of the museum will be built around them.
(bagpipes playing "America the Beautiful")
Almost 1,000 artifacts from September 11
will be on display at the museum.
This fire truck wrapped in plastic
is lowered through a hole in the roof, 70 feet down.
It's from the fire department's Ladder Company 3,
which lost 11 of its own while helping evacuate others.
Each artifact tells a story,
like this mangled piece of steel, called M2,
that was located where the first plane,
American Flight 11 from Boston, struck the North Tower.
It is a chilling reminder of the moment the attack started.
Now it is hoisted up and set in place.
Future generations need to understand
what took place down here.
When they see a piece of steel bent and twisted like that,
they can now begin to understand
the amount of destruction,
the amount of sadness that came upon this site.
NARRATOR: Next door at One World Trade Center,
a one-of-a-kind structure is taking shape.
20 stories high, the podium base is designed to be strong enough
to survive a massive truck bomb,
and unless the base of the building is super strong,
it could also be hard to attract renters.
The podium has thick concrete walls
that are reinforced with large steel columns.
Not only is it strong,
it will look strong enough to be a deterrent.
CHILDS: One of the things that I've learned about safety
is the appearance of safety.
If somebody looks at a building and says,
"Boy, that looks pretty flimsy," they are interested in it.
If it looks tremendously strong, you say,
"Well, let's go pick on somebody else."
NARRATOR: But there's a cost to this approach.
David Childs does not want to create a fortress.
In an attempt to make the podium more inviting,
he designs soaring entryways.
Behind them, giant concrete blast walls protect the lobby,
but Italian marble will hide their true purpose,
and large openings will allow sunlight to stream in.
CHILDS: Because of the nature of the destruction
that was here before, you don't want to give the impression
that this is a place of refuge and of fear.
You want it to be a sense of openness to it.
This building needs to appear open.
NARRATOR: So he decides to cover the podium
with a kind of glass that reflects light like a prism.
The glass will have to be cut
in a way that could compromise its strength.
It's a unique challenge, but not the only one.
Creating panels of glass big enough to start with
is also tricky.
JEFF YIGDALL: This glass is one-inch thick glass,
130 inches wide and 159 inches long.
Each individual piece of glass is 1,800 pounds,
almost a ton of glass in one single piece.
NARRATOR: To create these one-of-a-kind panels,
they start the old-fashioned way.
Take sand, combine it with other ingredients
like lime and baking soda, and put it in a furnace
at temperatures nearly 3000 degrees.
The intense heat turns the mix into liquid,
which is then poured onto molten tin.
The glass appears as a red line floating on top.
On rollers on a line almost a quarter of a mile long,
the glass cools and strengthens.
But if conditions aren't perfect, neither are the panels.
And you can hear that glass in the background
just going down.
(glass shattering)
So even though we look at this
as a momentary disaster in our process,
that told us what we need to do
to make the correction in an engineering sense.
NARRATOR: At the end, it's cut into those large panels.
Next, these enormous panes of glass are placed on ships
and sent halfway across the world to China,
where they designed special machines
to cut grooves into the glass.
But will it hold up?
For such a high-tech product,
the test is simple and revealing.
ALAIN LaPIERRE: Three... two... one...
NARRATOR: It's no surprise that it breaks,
but it's designed to stick together like safety glass.
Three... two... one.
NARRATOR: Instead, it shatters into dangerous shards.
LaPIERRE: All right.
As you can see, the debris are pretty big.
Something like that would fall on your head,
that would not be pleasant.
So this is why we do these kind of tests.
NARRATOR: When the results reach New York, the news is heartbreaking.
This building is David Childs' legacy.
He needs to find a new solution for the podium glass
that will be both safe and beautiful.
Above the podium, Childs is getting much better results.
One World Trade Center is rising a floor a week.
Inside, there is a steady rhythm of work:
build out the floors with concrete,
spray with fireproofing,
lay elevator tracks in the cores...
All the way, to the very top.
NARRATOR: As the core rises,
on the outside, One World Trade Center is starting to take on
its distinctive shape.
The podium is a square about the size of the original towers.
At the 20th floor, the corners taper in.
A square becomes an octagon.
Four sides become eight interlocking triangles.
Finally, at the top, it resolves in a square once again.
The profile, as you look from the memorial,
is identical to the old,
but as you walk around it, you see the corners tapering in.
It's a new modern building,
but it has a memory of what was lost.
NARRATOR: To achieve this subtle shape shift,
Childs turns to steel-- 45,000 tons of it.
CHILDS: Steel is relatively light.
It's flexible.
You can do all sorts of things with it.
It's supple.
It's a wonderful material.
NARRATOR: Almost a quarter of it, 10,000 tons, starts here:
Coatesville, Pennsylvania.
One World Trade Center is designed to be
a certified green building.
Steel contributes to that
because much of it comes from recycled materials
like old refrigerators, cars, even toasters,
all melted down into liquid.
Then it's poured and molded into giant sheets.
The sheets are carefully cut, welded and shaped
to make pieces that fit in a specific place in the building.
Some of the largest are called nodes.
They can be as large as 60 tons and stand three stories high.
Nodes are giant joints
that hold multiple pieces of steel together.
They come in all shapes and sizes
and make it possible for the building to shift form
from four sides into eight.
And they also help redistribute the weight
as the building rises.
Back at the site,
a critical node is ready to be hoisted into place.
Get it up close as you can to the rig!
NARRATOR: Working with steel this big takes experience.
Peter Jacobs is a member of the Mohawk nation,
famed for their work on skyscrapers and bridges
for over a century.
He is a fifth-generation ironworker,
a member of an elite group called the raising gang.
Their work starts at the base of the building,
where they move giant crane hooks,
called chokers, into place.
Two cranes lift the massive 40-foot high node
hundreds of feet up
as the raising gang guides it into place.
JACOBS: It's a dangerous job, connecting-- very.
It's the most dangerous job out of all of them.
If you ain't got the heart...
That's the whole key to it.
(pounding his chest)
Right in there.
NARRATOR: The work of the raising gang hasn't changed
since steel-frame construction began over a century ago.
Neither has the next gang
to take possession of the massive node:
the bolting gang.
Their job:
to mercilessly pound and bolt the node into place.
If things are off by one or two or three inches,
we bring out the big boy.
Show them the big boy.
The big boy's here.
That pulls the entire building into plumb.
NARRATOR: It's the plumb-up gang that makes sure every column
is perfectly plumb, perfectly vertical.
STEELWORKER: It's a game
of less than inches, it's a game of quarter inches.
NARRATOR: The plumbness of a building is critical.
STEELWORKER: Our tolerance is probably one inch on a column
and we try and keep everything
within a half-inch of where it's supposed to go.
So it's quarter-inches,
and eighths and sixteenths, it's not inches.
NARRATOR: The slightest mistake and the building will tilt.
Finally the welding gang completes the join.
WELDER: When you first start working, walking the steel,
you feel like, all right, looking around you,
look how high up I am.
But after a while, you start just...
you're focused on your work.
You really don't think too much that,
oh, you are 700, 800 feet in the air.
NARRATOR: A steelworker's nerve leads the way up a super skyscraper.
Story after story, the steel goes up.
The concrete core,
which gives One World Trade Center its strength,
follows several stories behind.
Until the core catches up, the steel frame needs stability.
To solve this problem, Larry Davis at DCM Erectors
comes up with a novel idea.
We saw this great big space and we said,
"Well, maybe we can put something in here."
NARRATOR: So Davis puts cargo containers between the steel beams
and outfits them with tables and chairs
where construction workers go on breaks.
He calls them hotels.
DAVIS: We built like a little city
where we have washrooms, workstations...
NARRATOR: Even a Subway shop, where crews go for lunch.
To go to the top with some of the hoists
took a substantial amount of time,
especially with 1,200 workers each and every day
moving around throughout the building, up and down.
NARRATOR: With only a half-hour for lunch
and up to an hour's commute
from the top of the building to the base,
the hotels are a real timesaver for workers.
So that's our accommodation for the job,
which works well because of the height of the building.
NARRATOR: Another problem building high:
equipment and tools can hurtle more than 1,000 feet
onto construction workers or pedestrians below.
To prevent this from happening,
Davis designed a fireproof steel-framed net
that covers the exterior of the top floors of construction.
DAVIS: The cocoon system provides tremendous worker safety
and prevents anything from coming off the building.
NARRATOR: The hotels, two cranes and the cocoon
climb the super skyscraper in unison.
DAVIS: We can climb the crane in two hours,
and we can climb all the hotels in four hours,
and the cocoons climb in about six hours.
NARRATOR: As One World Trade Center makes its way
into the New York City skyline,
right below,
another extraordinary structure is taking shape:
the 9/11 Memorial, the vision of architect Michael Arad.
This design calls for two pools
in the footprints of the original towers,
surrounded by a forest of trees.
It was an idea that was just in my head
and then on a piece of trace paper,
and then eventually I ended up building
a small fountain on my rooftop.
NARRATOR: He calls it "Reflecting Absence."
PAUL GOLDBERGER: Using the footprints of the two towers
as the starting point for the memorial
is actually very powerful symbolism.
Where there was presence, there is now absence;
where there was solid, there is now void.
NARRATOR: Each pool is 30,000 square feet.
VEGA: You could not imagine the scale of it
unless you're looking at it right here.
NARRATOR: They are lined with granite from a quarry in Virginia.
Almost 5,000 tiles must be laid in a specific order
so there is a continuous pattern to the grain.
VEGA: Just look at that stone.
If you could just imagine the lines not being there,
it looks like one stone.
Look at how that grain just flows.
It's almost as though this stone
is a continuation of this stone.
The adjacent piece looks like it belongs next to it.
NARRATOR: When the pools are complete, 52,000 gallons of water
will cascade over the walls every minute, drop 30 feet,
and disappear into a second, inner pool.
ARAD: We didn't want to create a torrent.
This is not about being behind Niagara Falls;
it was always about creating something
that is gentle yet persistent.
And then the question is, how do you make that idea take shape?
NARRATOR: The solution arrives on site.
It's called a weir.
Weirs are normally used to alter the flow of rivers
to prevent flooding.
But here they need to move water
into the shape of an architect's vision.
The weirs are there to push it outward
just far enough to give it a gentle arc
to make it fall in a neat cascade.
Now in place, the weirs are ready to be tested.
It's time to turn on the water.
Workers carefully watch as water starts to flow
through the system into the troughs by the side of the pool.
WORKER It's holding pretty good,
so we're going to go ahead and let it go over.
It's coming over there.
WORKER: It's starting to go over here, too.
Yeah, yeah.
That wall... the wind is doing it!
Here it goes!
ARAD: It's beautiful; it's moving.
I am... at a loss for words.
NARRATOR: But the hardest part is yet to come.
In Dover, New Jersey, powerful water jets engrave the names
of the 2,982 individuals whose lives were lost on 9/11.
The names are not listed alphabetically,
but by the locations where individuals died:
the South Tower, the North Tower,
Flights 11, 93, 77, 175 and the Pentagon.
First responders and those who died in the 1993 attacks
are also grouped together.
PAULA BERRY: It in essence does tell the story of what happened
largely by the way in which the names are arranged.
So when you go,
you will actually be able to sort of peel back
and understand the story a little better.
JIM MORETTI: 50% of the folks that are on the memorial,
no remains were found, and so this is going to be
for many families and many loved ones
the place that they will go on those special days,
the birthdays, the anniversaries.
Unfortunately, this is their final resting place.
FRANK ANDOLINO: It's heartbreaking, really,
to look at all these people
and the pain them and their families endured.
It's sad, it really is.
But we gotta get a job done.
NARRATOR: As 152 bronze panels are carefully etched,
hundreds of trees are being prepared
to be taken to their new home: Ground Zero.
They originally come from the three places where people died:
New York, Pennsylvania and the Washington, D.C., area.
They will become part of an eight-acre forest
on the Memorial Plaza.
Beneath the plaza,
a complex irrigation system has been devised
to bring water and fertilizer to each and every tree.
But what makes this system truly advanced
is the sensor technology embedded in the soil.
VEGA: These trees have
their own computer chip in them.
They have their own monitoring system
for aeration and irrigation.
I mean, each tree has its own little ecosystem,
so we know how they're doing.
It's all high tech, real high tech
and yet when you look at it,
it's just a beautiful little forest.
NARRATOR: 16 trees weighing 18,000 pounds each
are being hoisted and prepared to move.
VEGA: It's a magical time today.
There's nothing like planting a tree.
NARRATOR: The trees arrive at Ground Zero
just in time for the memorial to open
on the 10th anniversary of 9/11.
Â♪ O say, can you see
Â♪ By the dawn's...
DANIELS: The memorial is a place
of reflection and remembrance,
and really there's something positive
in that out of such tragedy,
we were able to do something that is really beautiful.
And for the families and friends of those who were lost,
it is a place to remember
the lives that these individuals lived.
NARRATOR: One of those individuals, David Berry,
was on the 93rd floor of the South Tower when it collapsed.
Ever since, his wife Paula has dedicated herself
to seeing the memorial come to fruition.
PAULA BERRY: I find it really heartening to see all these tourists come,
wrapped in ponchos, with their umbrellas,
knowing full well they're coming to see it in the rain.
This was a disaster area and then a construction site.
But I think it's become a place of contemplation.
People will take away the magnitude of the event
and the loss.
NARRATOR: By the tenth anniversary in 2011,
the supertower had reached 80 stories
and huge panels of glass were starting to cover the exterior.
Over the next several years,
these enormous panes of glass, called the curtain wall,
will make One World Trade Center impermeable
to the elements of its surroundings,
except for one...
Wind.
GOTTESDIENER: When you build buildings of this height,
you now begin dealing with a whole new set of criteria.
One of the things is the sway of the building,
and that sway comes from wind--
the wind pushing it back and forth.
NARRATOR: When wind hits a rectangular skyscraper,
it pushes against the flat surface
and creates turbulence around the sides,
and that causes the building to sway.
But One World Trade Center's unique design
means the wind is not a problem.
CHILDS: This building is tapered
at the corners
so that as the wind hits the top, it confuses the wind.
NARRATOR: Instead of hitting a broad, flat surface,
the wind flows around the tapered corners
in a more gentle way,
and that reduces the turbulence and the sway.
And there's another reason
this supertower has so little movement.
GOTTESDIENER: The building has so much redundancy of structure
and strength at the core of that center spine
with concrete supporting it,
it naturally is a very, very stiff building.
NARRATOR: At its base, where its builders claim One World Trade Center
is stronger than any skyscraper ever built,
a solution has finally been found to the prismatic glass...
(glass shattering)
...which shattered when put to the test.
GOTTESDIENER: This is a small sample of the glass,
and it's literally three layers of glass laminated together,
different qualities of glass and thickness
for strength and rigidity.
But what happens is you get this beautiful quality
and beautiful opulence to the glass.
NARRATOR: Over the next few months, thousands of panels of glass
will cover the entire base of the building.
But unlike the curtain wall above, they're not flat.
In order to let air
in and out of the mechanical systems behind them,
the panels open up.
It's not just a skin, but there's a depth to it.
It gives you the opportunity of being something
which is breathable and open and, in a way, welcoming.
NARRATOR: Although this podium glass
was not David Childs' original vision,
he knows that no project as complex and innovative as this
can be completed without its trials.
CHILDS: At the end of the day, nobody will recognize
all of those trials and difficulties
of getting these things all to be solved in a simple building,
but to have this building as a serene a form as possible
was terribly important to me as the designer.
NARRATOR: By the summer of 2013,
the 9/11 Museum is also on its way to completion,
scheduled to open in several months.
Wow, this is so different from when I was here last.
It really is beginning to look like a museum.
And you can see how huge this space is.
It is cavernous.
This is an overlook,
the first time you get to see the slurry walls,
and it always sends chills up my spine.
This to me is... resilience.
This is resilience.
These are the survivor's staircase.
Many people within the building used these stairs to get out.
They represent, um...
They represent those people who were saved.
DANIELS: When people come to this museum and they see
the worst of humanity in the attacks that took place,
they're also going to see the best of humanity.
The first responder vehicles that we have in this museum,
they are so powerful because they tell the story
of the sacrifice and selflessness of so many.
And I think for our children,
for people from around the world,
knowing that, it's a comforting thing.
NARRATOR: Just before winter descends on the New York Harbor,
a barge makes its way down the Hudson River,
past the Statue of Liberty.
It is carrying precious cargo:
the first nine sections of the One World Trade Center spire.
It has taken a month for them to make their way from Quebec
to their final destination: Ground Zero.
The next morning, the heaviest piece, the 67-ton base,
is lifted to the roof, 1,368 feet.
WORKER: It's nice to be a part of it.
Finally we're reaching it,
and it's symbolic, everybody knows that,
so I'm excited and proud to be here.
NARRATOR: Over the next several months,
the remaining 15 sections of spire are lifted
to the top of the supertower and assembled.
WORKER: It just means the world.
It's a major step forward.
It just puts everything back to where it should be.
NARRATOR: And finally, the last two sections of the spire,
including the beacon, are lifted to reach a symbolic 1,776 feet.
For the thousands of workers who built this tower,
it's a moment to savor.
PATRICK FOYE: When it was bolted into place,
the construction workers and everybody on the roof
spontaneously broke into cheers and applause.
It was a breathtaking moment.
NARRATOR: On the 12th anniversary of 9/11,
construction at One World Trade Center is almost finished.
Ground Zero is nearing completion.
The end is in sight.
Yeah, it's going to be one hell of a landmark, you know.
Because you can go back,
point it out to your kids or your grandkids someday
and say, "I worked on that.
I helped build that building," you know.
NARRATOR: Already people are visiting here from all over the world.
Soon they will work here.
Life has returned to Ground Zero.
People will know intuitively where they are
when they come here.
They'll know what was here,
they'll know the loss that is here,
and yes, you still feel that loss,
but it's a place of healing.
NARRATOR: In years to come,
this sacred ground will take on new meaning
that we can't now foresee.
But the way Ground Zero has been designed and built
makes one thing certain:
what happened here will never be forgotten.
This NOVA program is available on DVD.
To order, visit shoppbs.org, or call 1-800-playpbs.
NOVA is also available for download on iTunes.
Captioned by Media Access Group at WGBH access.wgbh.org