Original subtitles

And oxygen that ultimately eat away at steel.

Narrator: The recipe for steel is simple --

Heat iron ore until liquefied, boil out impurities,

Add some carbon for strength,

Then let it solidify into whatever shape you desire.

And if we want our bridge to last,

It's going to take some work.

So steel will be coated in paint systems.

Paint systems will not last for 200 years on their own.

You'll require touch-ups and repairs

And possibly re-coating

Throughout the life of the structure.

Narrator: Paint protects against the humidity

You really had not had steel used at this scale before.

Now, what about the deck of the bridge?

This will be a massive undertaking.

And back in the lab, mamdouh el-badry is working

On a state-of-the-art solution to solve that problem.

The composite materials el-badry's using promise

To make his bridge system invincible.

So why don't we build the super-bridge of the future

Out of el-badry's super strong composite?

Well, we could.

But we wouldn't necessarily achieve the performance

That we're looking for right now.

I think we also have to look at not

So today, we could definitely use granite,

Narrator: We need our towers to be strong and stately,

Not crumbling and corroding.

In canada, mamdouh el-badry is addressing the problem

In a lab at the university of calgary.

He's swapping traditional rebar

For a mix of fiberglass, plastic, and carbon.

So if we use corrosion-free composite rebar reinforcement,

We can build our towers from concrete.

But how's that going to look

Next to this icon of architecture?

We would like to have a look that blends

With an older environment.

Just the strength of the materials,

But we most likely would use it as a facing.

And granite facing becomes very beautiful.

Narrator: Got it -- modern-day muscle inside

And classic good looks outside.

Next up, we need to string our cables

And build our bridge deck.

♪

To do that, we'll use the molten material

That forms the backbone of the brooklyn bridge -- steel.

John roebling, in particular, pushed forward steel wire.

And this was the first steel-wire bridge.

We still have to do, you know, the physical test.

Taken to ensure environmental compliance.

Narrator: Todays engineers test for environmental impact

As well as safety.

John roebling was intuitive of the aerodynamic analysis

And the situation that he knew was prevalent,

But couldn't put numbers to it.

So today, we take the bridge that we want to build

And we use a model that's exact-scale,

Put it in a wind-tunnel test,

And that information is hugely important to the analysis.

So even with our sophisticated modelling --

Which gets us almost there but not quite --

Because there's a lot more steps

Narrator: Mamdouh el-badry's been working on this prototype

For more than 15 years.

The good news -- his trusses are tough.

♪

We are loading the girder and the deck, actually, with

Cycles of loading simulating traffic on the bridge.

And then we are kind of measuring

How many million cycles

The girder and the deck will survive.

Narrator: While billions of simulated sedans

Put these girders through the motions,

A second prototype is chilling in here.

Now we need to figure out who is going to build it.

But also the stiffness.

No one likes bendy, flexible bridges.

They're unnerving.

And fiber composites often have --

Are more flexible than steel and concrete equivalents.

Narrator: El-badry has the solution.

So, the best way to utilize them is actually to combine them

With the conventional materials

To make a hybrid system like the one that I have developed.

So we're going to build two new bridges

Out of a blend of materials

That will set a new standard in bridge architecture.

And it does look a bit disturbing after a while.

Narrator: We're going to turn the old brooklyn bridge

Into a pedestrian walkway

And build two brand-new bridges on either side.

Our design experts said we ought to opt

For a cable-stayed bridge made of concrete,

Steel, stone facing,

And state-of-the-art composite materials.

So we must be ready to build now, right?

Not so fast.

Scollard: Preparation time today

Is a lot longer than it used to be

Once you have the towers up, you can start erecting the deck.

When gertie collapsed,

More than 1,500 people have been killed

In bridge failures in this century alone.

That can't happen to our new brooklyn bridges.

We need to find the world's best engineers and ask them,

Should we build a cable-stayed or suspension bridge?

Scollard: A lot of it comes down to the cost.

And a big difference between a cable-stayed bridge

And the suspension bridge

Is usually the duration of construction.

Cable-stayed bridges can typically be built

One year faster than a suspension bridge can be.

Narrator: Though thankfully no one died

And so as you put in the cables,

You are progressively putting in the deck at the same time.

And so there's more operations being done in parallel,

Rather than in sequence.

Narrator: It seems that a cable-stayed bridge

Is the way to go.

But will we ever be able to match

The original brooklyn beauty?

Aesthetics is personal and subjective, but forgive me --

I can't imagine looking at that structure

And not just being in awe.

♪

But the biggest problem was the girders.

Roebling's zeal for safety.

♪

The tacoma narrows bridge in washington,

Nicknamed "galloping gertie"

Because of the unintended undulations

Experienced during high winds,

Was the third-longest bridge in the world

When it opened in 1940.

Four months later, it collapsed.

What went wrong?

The bridge was too narrow for its length,

And the towers weren't strong enough.

Narrator: It's a hard act to follow,

Every long-span bridge has girders --

Horizontal beams that help hold the weight of the deck.

Gertie's were tall and made from solid metal,

Which caught the wind like a sail --

A major misunderstanding of aerodynamics.

Engineers look to this bridge

For an example of what not to do.

Scollard: Engineers have a professional responsibility

Not to do things that they aren't certain will work out.

A mistake by a surgeon would perhaps hurt one person.

Our mistakes can kill a number of people.

Narrator: To avoid stone's hefty weight and expense,

Is a towering task.

There is limestone, there's granite, and it's masonry.

It's stone.

Narrator: Stone has proven its durability throughout time

And all over the world.

But our modern-day engineers

Are wary of creating a money pit.

Granite is an expensive material.

And considered on the scale of a bridge tower,

It would be prohibitive in itself.

You imagine how heavy the granite and limestone towers

Would be at the end?

Narrator: And topping these stately pillars

Most bridge towers today

Are built with steel or steel-reinforced concrete.

Nowadays, we would use high-performance concrete

With high-strength steel bars,

Which gives us the capacity to resist loads better.

Narrator: But this method comes with its own challenges.

The big problem with concrete that we see in towers now

Is actually the reinforcement corroding.

Once the steel corrodes and starts expanding

With rust layers,

It pops off the concrete that's surrounding it

Are probably the key determinants of the life

But modern-engineering smarts

Seem to produce knockout good looks.

The purest form of bridge aesthetics

Is to design a clean, simple structure

Where the elements follow the natural load paths

That are required.

Structurally efficient design is inherently

Aesthetically pleasing.

Narrator: We'll plan for two new bridges --

One on each side that compliment

But don't interfere with the existing bridge.

Choosing the right materials and construction quality control

El-badry: So, this is an environmental chamber

That you actually get out of the bridge.

Narrator: We want our new bridges to be an icon

For centuries to come.

And that challenge begins with our towers.

Narrator: At 278 feet tall apiece,

The brooklyn bridge's gothic-style towers

Are two of its most recognizable features.

And they're crucial.

The towers for a suspension bridge,

And even for a cable-stayed bridge,

Really define the structure quite a bit.

And state-of-the-art composites to do it.

Narrator: And when the whole thing is done,

We'll re-create the same grand parade

That crossed the original brooklyn bridge.

A herd of elephants will show the world

The strength of our new span.

[ elephants trumpet ]

♪

♪

We did it!

We built two new brooklyn bridges over the east river.

They're cable-stayed bridges,

And we've used concrete, stone, steel,

Painting the lines on the roadway, and things like that.

With all the testing and preparation, it took 14 years.

In total, 750 people worked on the project.

So, how does the cost of our new bridge

Compare to the cost of the original?

The $15.5 million construction cost in --

In the late 1800s nowadays would be the equivalent

Of about $1.3 billion.

And based on similarly complex projects

And similarly large projects,

I would certainly say it's more than $1 billion.

$2 billion would be a good starting place.

Narrator: But not everyone's convinced that $2 billion

And then hang the deck truss segments from them.

And preparing of the site for the actual construction.

Narrator: Next, it's time to build our towers.

Then typically, the construction goes from the bottom up.

So the first thing would be to install all of the foundations,

And then getting above the ground,

They would build the towers.

Narrator: After the towers are erected,

We've got to string the cables.

So, how did they do that for the brooklyn bridge?

After the towers reached the -- their top height,

Then the steel cables would've been hung across the river.

With the steel cables in place, they could place the suspenders

Is going to fit the bill.

Narrator: But remember, we're building a cable-stayed bridge.

And we can build that even faster.

With a cable-stayed bridge,

Once you have the towers up, you can start erecting the deck.

And so as you put in the cables,

You are progressively putting in the deck at the same time.

Narrator: With the deck in place,

We're almost ready for rush hour.

There would be the finishing works

To actually prepare the bridge for use --

Tying it into the rest of the roads, putting on the barriers,

And engineers tend to -- to be experts in math and science.

And I hope it will outlive my children.

Beyond that, I don't think any of us can imagine.

But you know, the future is a mystery.

We can see where we've been with great clarity.

We have only the dimmest idea of what's coming.

Narrator: No matter its life span,

The brooklyn bridge will live on as a beacon of inspiration.

Bridges are actually, perhaps, the only structure

That stimulates imagination, creativity.

Scollard: Bridges are complex objects.

They look simple, but there's actually a lot of complex work

That goes into them.

I certainly hope it will outlive me,

It's that math and science that allows us to do it

In a safe and efficient way.

Narrator: Icons of civic infrastructure

Like the brooklyn bridge

Don't build themselves.

It takes hard-working men and women,

Brilliant innovators, and big dreamers.

The brooklyn bridge reminds us

That what seemed impossible yesterday

May be possible tomorrow.

And we can always find a way to connect our communities

And our cities if we built it today.

Inspired by the city's high line project.

One of the most endearing qualities about engineers

Is their optimism.

And you need that optimism to get anything built.

But they're often dead wrong

About what the costs of their projects will be.

The brooklyn bridge cost three times

What people thought it would cost back in the 19th century.

Narrator: So let's triple it.

For $6 billion, we can build two new brooklyn bridges.

But we're not done yet.

We've still got to pay to transform

The old brooklyn bridge into a pedestrian walkway

Of the construction team and the clearing

The way we see it, it's worth blowing the budget

To give a second life

To a walkway with a million-dollar view.

There is definitely an important reason

To try to keep this bridge as it is and rehabilitate it.

Narrator: But will there come a day

When the brooklyn bridge can't be saved?

No owner of a bridge or developer of a bridge

Is looking for forever.

I would say, I don't think there's an end in sight

For the brooklyn bridge.

We don't read about all of the assistant engineers,

But remember, washington roebling ended up bedridden.

And so his responsibilities in the field

Fell to his wife, emily.

Barbas: Emily roebling was the eyes and ears of her disabled husband.

She was the one who had to take the design

And make sure those instructions were implemented in the field.

In the late 1800s,

It was unheard of for a woman to be in that position.

Narrator: But building the brooklyn bridge took more than a great family.

It took a massive team.

When we read the history about the brooklyn bridge,

We read about the key figures.

In design and construction, as well.

All of the field engineers, all of the people on-site

Actually overseeing the work and making it happen.

Narrator: It took an untold number of construction workers

To build the brooklyn bridge.

And at the bottom of it all were the so-called sandhogs.

Baker: The people who built the bridge

Were some of the earliest sandhogs --

Some of the same amazing tribe

Who would build the subway

And many of the tunnels under the rivers.

Narrator: To this day, sandhogs can still be found

Working below grade.

Narrator: So we're facing 11 years of project development

That we actually put the prototype inside

And subject them to cycles of temperature

Between cold and warm.

Narrator: Our bridges will stand up to the weather, too.

This process definitely takes time.

But does it actually take longer to build bridges today

Than in the 19th century?

The brooklyn bridge took 14 years to build,

Which is, by modern standards, a very long time.

Overall length of development is probably similar

To what it was at the time of the brooklyn bridge,

But it's spent differently.

This is the construction force

And three years of construction --

14 years altogether, just like the original brooklyn bridge.

We've got our design plans.

We've picked our materials.

Now we have to put together the workforce we need

To get the job done.

First thing -- we need to find a team of engineers

To rival the family firm that built the brooklyn bridge.

The family that actually designed

And built the brooklyn bridge -- they were completely in charge

Because the head of the family was expert

To alleviate traffic between brooklyn and manhattan.

In the field day-in and day-out,

Providing labor and actually doing the work.

Narrator: So let's put it at 100 workers

For the 14-year duration of the project,

And another 650 people to come in

During the three-year construction phase.

That's 750 people total.

At industry wages,

We're looking at a labor bill of $335 million.

Now it's time for the finishing touches

Before we can unveil our masterpiece to the public.

Narrator: We're imagining a 21st century roadway

Of that, about 650 of them are actually working

It will be made of the strongest,

Most durable materials --

Concrete, plastics, stone, and steel.

And it will take 750 workers

And 14 years to plan and construct this beast.

We've got our team in place,

And their first job is to demolish enough

East river real estate to make room for our bridge towers.

Scollard: Most bridge construction projects

Probably have five key stages.

The first is gonna be the mobilization

In the latest safety equipment.

That specializes in working underground.

If it looks like a tough job today,

Imagine the conditions a century ago.

They tended to be local residents,

So a lot of them were immigrants.

They worked very cheap -- $2.75 for a four-hour shift

In which you risked your life.

20 to 40 of them died building the bridge.

And just the vagueness of that number gives you an indication

As to how little their lives were valued.

20, 40, who knew?

Narrator: Our modern-day bridge builders will be outfitted

Narrator: Unfortunately, not all of them inherited

When the brooklyn bridge was being constructed,

There was not the kind of regulation we have today.

And workers did not even have hard hats or boots.

They came to work dressed in white-collared shirts

And maybe a top hat,

And workers were often not paid fair wages.

Narrator: When hiring our workforce,

It's wise to take a lead

From the team overseeing the new tappan zee bridge.

How many people does it take to build a bridge nowadays?

We have about 750 people working on the project.

Brooklyn was a separate city --

Safety culture in construction is very different.

Narrator: It took 14 years to build the first brooklyn bridge.

Can we build a new one even faster?

How hard can that be?

To find out, we'll have to line up all the parts, pieces,

And people we'd need in order to get the job done.

♪

Back in the 1860s, it took more than a new york minute

To catch a ferry between brooklyn and new york.

Baker: The millions of new yorkers who commuted from brooklyn

Were tired of waiting out in the cold.

In the 1880s when the brooklyn bridge was going up,

Scollard: No injury, no loss of life is acceptable.

The third-largest city in the country.

New york was the first -- just manhattan --

Then chicago, then brooklyn.

Ferries ran every 10 minutes, but still,

Out here on the river,

It was quite a cold process.

So they wanted to build the bridge

To really connect the two cities.

Narrator: But not everyone was pleased with the merge.

Robins: There were people in brooklyn

Who opposed the building of the bridge.

"you build that bridge,

It's in a densely populated urban area on both

Well, we may not have a choice.

The brooklyn bridge is getting old,

And billions of dollars are being spent on life support

For this aging landmark, leaving some to wonder

If it wouldn't be more fiscally responsible

To tear it down and start over.

♪

Narrator: The brooklyn bridge may be beautiful, iconic,

And a marvel of its age.

But the bridges we build today are longer, wider, and taller.

Maybe we can learn something from them.

But replacing an icon is not going to be cheap.

And new york will swallow brooklyn."

The manhattan and the brooklyn side.

So the construction will be -- will be expensive.

Would certainly say it's more than $1 billion.

Narrator: And money may be the least of our problems.

♪

We've got to decide what kind of bridge we're building here,

And what we're going to build it out of.

I think going forward, it's gonna be so exciting

Because we can really push the envelope.

Narrator: We may be able to push the envelope,

But we definitely cannot stretch the safety rules.

The brooklyn bridge has provided new yorkers

Narrator: And, believe it or not,

The perfect location is exactly where the original bridge lives.

Can't we just demolish it and start again?

Robins: You have to look at the larger picture.

You have to recognize that there is a cost benefit

To having the brooklyn bridge standing,

And you need to throw that into the calculations before deciding

Whether it makes sense financially to rip it down.

Narrator: With current technology,

Is there a way to build around the old bridge

And still solve the modern-day traffic debacle?

Narrator: Since its construction in 1883,

Do we want to build the bridge in the same place?

With a convenient crossing over the east river.

But traffic has become a major issue,

So we're going to see if we can build a new, better bridge.

And instead of tearing down the old icon,

We're trying to give it new life.

Robins: Should the time come that the brooklyn bridge

Can't support traffic for some reason --

Meaning automobile traffic --

It will do just fine as a pedestrian bridge.

Narrator: 7,000 people already cross the brooklyn bridge

By foot every day on a roadway above the cars.

Maybe we can upgrade their experience.

And built to last.

And that is, in fact, what happened.

Narrator: The brooklyn bridge completely transformed new york.

But the problem it was built to solve --

Traffic --

Is now worse than ever,

Thanks in part to a growing population.

There's just been massive, massive delays and problems

With just commuting on a basic level.

Narrator: But maybe we can help.

If we re-create a 19th century icon

To break up a 21st century traffic jam,

Our new bridge has got to be beautiful, brag-worthy,

Narrator: But could we build the brooklyn bridge today?

And that mission will guide every decision we make

On our modern-day brooklyn bridge.

Where are we going to build it?

What kind of bridge are we building?

What materials are we building it out of?

How long is it going to take, how many people,

And how much will whole thing cost?

But first thing's first.

We've got to know where we're going to build it.

If I were tasked to build the brooklyn bridge today,

I think at first I'd have to really figure out,

Could we even do it if we built it today?

Narrator: What have we learned

Since the bridge was originally built?

We're going to see if we can do it better

Using the heaviest equipment, the latest technology,

And an unlimited budget.

Choosing the right materials and construction quality control

Are probably the key determinants of the life

That you actually get out of the bridge.

Plastic is always stronger than steel.

Narrator: We're on the jobsite of one of the world's greatest wonders.

And we're wondering -- how long would it take,

How much would it cost, how many workers would we need?

That are more in need of repair?

-- Captions by vitac -- www.Vitac.Com

Captions paid for by discovery communications

New york, new york --

Where the most ambitious dreamers come to make it big.

And back in 1869 when ground broke on the brooklyn bridge,

The big apple got a little bigger.

This was gonna be far

And away the biggest suspension bridge in the world,

And it turned out to be so -- 5,989 feet.

Narrator: Flip the brooklyn bridge upright,

And it's as tall as five empire state buildings.

Its gothic-style towers reach

They were new.

One of america's finest architectural achievements,

Proudly connecting brooklyn to the island of manhattan

Since 1883.

The brooklyn bridge is the brooklyn bridge.

There's no bridge quite like it.

El-badry: At the time that brooklyn bridge was built,

It was something completely new, completely innovative.

There are features that handle wind loads

In such a way that is genius.

Narrator: Yet constructing this masterpiece came at a price.

It hadn't been done before.

And the techniques -- they weren't tested.

As high as new york's first skyscrapers --

And in many cases, they were risky, as well.

Back in the day in the late 1880s,

There was not the kind of regulation we have today.

20 to 40 of them died building the bridge.

Narrator: And maintaining the bridge for commuters

And pedestrians is an expensive venture.

Blau: It could go up to about $500 million.

There was a massive, massive overhaul.

I mean, there was peeling paint, there was holes in the --

Like, in the steel.

Can that money be spent for assets

So the idea that it couldn't be built

And smashes into the dock.

It smashes the toes on one of his feet,

Which would've been all right

Except he insisted on only applying his water cure to it.

Well, after lockjaw and a coma of several days, he died.

And responsibility for building the bridge --

Most of the building of the bridge --

Went to his son, washington roebling.

Narrator: By 1869,

The brooklyn bridge's chief engineer was gone.

But this construction project wasn't going away.

Scollard: It hadn't been done before.

One of the ferries comes in too hard

Was actually very nearly true -- very difficult work environment,

Very risky in terms of the construction.

Narrator: To many, it's the most important bridge ever built --

An inspiration to engineers around the world.

El-badry: At the time that brooklyn bridge was built,

It was something completely new, completely innovative.

Barbas: They did not yet understand

Aerodynamic effects at that time.

Yet if you look at the brooklyn bridge,

There are features that handle wind loads

In such a way that is genius.

Helped shape new york city's skyline and self-image.

Two-thirds the height of the great pyramid of giza.

The seven-story-high towers were the --

Were the largest buildings built in america to that point.

Narrator: Cathedral-like arches support massive steel cables

300 feet above the east river.

Baker: The main cables -- there are four of them --

Are almost 16 inches thick.

And inside them are 5,434 separate pieces of steel wire.

There's enough wire in the bridge cables

To go across the united states and then some --

Over 3,500 miles of steel wire.

Narrator: There's no question that the brooklyn bridge

We're picturing something like this --

Robins: The brooklyn bridge is probably the most famous

Of all our bridges --

Probably because of its technological breakthroughs,

Because it linked the two cities,

Because it led to the creation of the city of greater new york,

But just because it's so beautiful.

Narrator: But this symbol of human achievement

Had an unlikely beginning.

The engineering genius behind it,

John augustus roebling, goes and surveys it.

And in a bit of poetic vengeance,

Using new technology in the construction,

Narrator: 25 years after the brooklyn bridge opened,

The manhattan, willamsburg, and queensboro bridges

Were also spanning the east river.

Many of these bridges incorporated

The suspension design pioneered by john a. Roebling.

But today, you can find bridges of all shapes and sizes.

If you look at the bridges that are being built right now

Throughout the world, there are lots of innovations in them.

And the innovation comes actually from the best systems

Used from this type of bridge and that type of bridge.

Perhaps these ideas will lead to a new type of bridge,

A new structure system, built of new materials,

Their location, their visibility, and their design.

And this can actually be an iconic bridge,

As well, for the future.

Narrator: So, what kind of bridge is best for our needs,

And will it ever be able to live up to the great lengths

That the brooklyn bridge reached?

To find out, we'll need to bridge past and present

By going back to the basics.

Narrator: The brooklyn bridge may be one of

The most iconic bridges in the world.

Yet it was built on years of engineering know-how.

The earliest bridges were beam bridges,

As simple as a tree trunk

Could they have bridged completely over the water?

Or concrete pilings have their -- their place.

But it's really gonna depend on the particular

Ground conditions at the site.

Narrator: Is our foundation going to be a boxy caisson

Or a long pile?

Turns out, thanks to modern engineering,

We have a third option.

You might still revisit that decision and see

Whether there's opportunity to pull the towers

Out of the -- the water.

The brooklyn bridge had their foundations in the waters,

Because they could span only so much at that time.

Stretching across a babbling brook.

Today, we can.

Generally speaking, it will simplify construction,

Lessen the environmental footprint for the project

Because you're not doing all of that in-water work.

Narrator: We're going to build more efficiently

By constructing on land.

But what are these bridges going to look like?

Robins: There are something like 6,000 bridges

Of all sizes in new york.

But most of them are unknown.

A few of them are just so iconic because of their size,

With that conservatism.

In that it has both parallel,

Traditional suspension cable systems as well as stay cables.

Narrator: A cable-stay bridge is supported by cables

Tied between the bridge deck and the towers,

While a suspension bridge is more like a clothesline.

Horizontal wire is strung between two towers,

Which in turn support the vertical wires

That carry the load of the deck.

It's kind of a hybrid system

That takes advantage of the two systems

Together to build a better bridge.

Brooklyn bridge was intentionally designed

Scollard: The brooklyn bridge is actually quite unique

You read reports that it was designed for six times

The load that it was actually anticipated to carry.

Narrator: Spanning the east river is an innovation

That propelled engineering into the 20th century.

This is really a test case.

And you build all kinds of incredible things such as

The golden gate bridge in san francisco,

Which is the first suspension bridge of that size

Built on what's actually the open ocean.

So this is something that teaches generations

Of american engineers.

He perfected the suspension bridge.

Then came arch bridges,

A favorite of the ancient romans.

This design made it possible to span greater distances

By distributing the weight over signature curves.

The next innovation was this system of load-bearing triangles

And squares called a truss,

Similar to the popsicle-stick bridges

You probably built back in school.

♪

And when john a. Roebling moved to the u.S.

From germany in 1831,

He wrote the next chapter in the history of bridges.

In modern construction, both caissons and steel

Scollard: The idea of building a suspension bridge

Was not unique, but pretty new.

Narrator: Roebling built suspension bridges

In pittsburgh, delaware, niagara falls,

And then this colorfully restored bridge

Across the ohio river.

But the brooklyn bridge was his most ambitious design.

It's the most famous suspension bridge in the world.

But ask an engineer about it,

And they'll let you in on a secret --

Roebling also used what are called stay cables.

And what we all strive to do is get out of the water.

Open to traffic.

It's been open for a year now.

And we're getting ready later this year

To open the second bridge to traffic.

Narrator: The new bridge,

Named after former new york governor mario m. Cuomo,

Is almost three times longer than the brooklyn bridge.

Work began by building a foundation

In the middle of the river.

That's where our new bridge will get started, as well.

Kick: For the construction of the new bridge,

It all starts in the water.

We have one of the parallel cable-stayed bridges

Right here, we're right in front of the main stand.

And this is one of our pylon piers.

These were some of the most challenging

Substructure elements that we had to construct.

Barbas: We have about 700 feet of very, very poor soil.

And the engineers had to design foundations

That were quite innovative in terms of steel diameter piles

That would go down maybe 300-plus feet

And rely on friction, because they couldn't get to bedrock.

Narrator: It's called a friction pile foundation.

Here's how it works.

Imagine a super thick chocolate milkshake.

We'll build two brand-new bridges for commuting --

Manhattan's high line, an elevated rail line

That's been transformed into a pedestrian paradise.

Blau: I mean, they've literally just converted

Into the most amazing thing

Where you can kind of look over the city.

And it was kind of the most --

Kind of for lack of better terms --

A sort of urban blight from before.

Narrator: So we'll keep the existing brooklyn bridge

And give it a makeover.

To address the traffic jam,

We'll build a new marvel on the same stretch of land.

Stick in a straw, and try to balance a credit card on top.

One westbound, one eastbound,

On either side of the current one.

Before we start building our new bridge,

We can learn a thing or two from another project.

Man: Three, two, one, ignition, fire.

Narrator: Just one hour upstate,

The six-decade old tappan zee bridge is being demolished

And replaced with a brand-new bridge.

Barbas: It was becoming extremely expensive

To rehabilitate the existing bridge.

We are fully into construction, quite in the later stages.

When workers came up doubled over in pain,

And they lowered it to the riverbed.

And workers went in.

Air was put in there so that it would keep the water out,

But also so the workers could breathe.

And they would excavate and take up all the soil and the muck.

Narrator: Although it seemed like a good idea at the time,

This pine box was actually quite dangerous.

Baker: You had to deal with going deep under water

In these highly pressurized, highly dangerous situations.

Nitrogen builds up in your blood,

And you need about 20 minutes at this level to decompress.

They did not understand this.

Barbas: So they put this box,

They called it caisson disease.

Turns out, it was the bends from coming up too fast

From underwater -- nitrogen in the blood.

Narrator: Among the afflicted

Was chief engineer washington roebling.

He watched the rest of his father's bridge go up

From his sickbed.

Now, in the 21st century,

We need to solve a similar problem.

What kind of foundation are we going to use?

♪

Which is drastically different

The straw is the pile, and the credit card is the pier.

The structure is unstable and won't support any weight.

Now, imagine two, four, or even eight straws doing the same job.

The stability increases,

And the credit card is able to bear a load.

That's how the cuomo -- or new tappan zee bridge --

Works, except with 1,220 piles

Each about the length of a football field

And built out of more than 100,000 tons of steel

And concrete.

Kick: We decided to use steel pipe pile foundations

To limit the amount of water work that had to be performed,

Narrator: The brooklyn bridge --

Than building a bridge in the old days,

Like when the brooklyn bridge was built

And they were forced to utilize caisson.

The caisson style of construction

That the brooklyn bridge employed

Was really like using --

Was yellow pine wood like an inverted giant box

Where the opening is at the bottom.

Narrator: It's true.

The brooklyn bridge sits on top of a wooden box

Filled with concrete.