Nova (1974–…): Season 44, Episode 4 - Super Tunnel - full transcript

Follow an army of engineers and designers as they tackle the complex challenge of building Crossrail, a massive new subterranean railway deep beneath the streets of London.

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NARRATOR:
Underneath the streets
of London,

an army of more than
10,000 engineers

is building a brand new
subterranean railway.

Okay!

MAN:
We've done the maths,

we've checked the maths,

and we've checked them
a third time.

NARRATOR:
Costing almost $23 billion,

it's the biggest
construction project in Europe.

I've been doing civil
engineering for 35 or so years.

Even I can't appreciate
the scale



until I come down here.

NARRATOR:
Workers are digging
26 miles of tunnels

and constructing ten
vast new stations

all under a tight deadline.

WOMAN:
You need to get
out of the way here,

because trains are gonna start
coming through.

NARRATOR:
They're over halfway through
a ten-year project.

That's ready to start pumping!

NARRATOR:
In a constant battle
to keep the city moving.

MAN:
Constructing Crossrail is like
undertaking open-heart surgery

on a patient
whilst that patient is awake.

NARRATOR:
The oldest rapid transit system
in the world,

the famed London Underground
is growing even bigger:

75 new miles of railway



in the midst of a city
that never stops.

Inside the "Super Tunnel,"
right now on NOVA.

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ople.

The key to keeping
everyone moving: the Tube.

The London Underground was
the world's first metro system,

a vast subterranean rail network

handling over a billion journeys
a year.

It's made up of ten
separate railway lines

that snake
right underneath the city.

A network of escalators
and walkways allow commuters

to disembark from one line
and board another

to travel in any direction
across the capital.

Victorian engineers opened
the first line here in 1863

at an estimated cost
of a million pounds.

It was built to solve
what was, even then,

London's massive
traffic problem.

To build it, engineers
closed streets for years,

cutting huge trenches,
laying track,

then covering the holes
back up again.

Today, the traffic in London
has gotten even worse.

(horn honking)

CABBIE:
You just gotta keep your cool

and just go with the flow,

not get too stressed out
about it all,

because you'll just
drive yourself mad.

(horn honking)

NARRATOR:
This makes the Tube
even more important--

and crowded.

The 150-year-old network

struggles to cope
with peak demand.

So today, engineers
are building

a brand-new underground
railway line

to help relieve the strain.

It will stretch
right across the city,

from the east to the west.

It's called Crossrail.

It will run overground

from Heathrow Airport
in the west

in a new tunnel
under Central London

connecting into existing
metro stations.

It will link shopping
and theater districts

in the West End

to the new financial district
of Canary Wharf

and terminate 14 miles east
of the city center.

It must link seamlessly
to the rest of the Tube

and be ready for passengers
in 2018.

If all goes well, Heathrow,
Europe's busiest airport,

will be just 28 minutes
from London's West End,

a journey that currently takes
almost an hour on the Tube.

An idea born in 1974,

Crossrail is now the biggest
engineering project in Europe.

Building Crossrail
in the middle of nowhere

would be a big enough technical
challenge, but to do that

right in the center of London

with all of the neighbors
above us and around us

makes it more complex still.

NARRATOR:
Today, there are 40 worksites
spread out across London.

Some are little more than shafts
allowing access

to the new train tunnels
growing underground.

Others are giant holes
puncturing the landscape,

forming the outlines
of ten new stations.

The sites in Central London
are hemmed in

between office buildings,
busy shops,

and heavily congested roads.

And that's just at street level.

Things get even tighter
underground.

This is Oxford Street,

the heart of the London
shopping district.

It's the busiest
commercial street in Europe.

Home to flagship stores

including the legendary
Selfridges department store,

200 million people visit
Oxford Street each year.

Few shoppers here
would ever suspect

that just 80 feet below,

a 500-member team
of engineers and builders

is chewing through the earth.

Tunnel construction manager
Steve Parker

keeps the project moving,

hopefully without disrupting
life on the street above.

PARKER:
In the future, I want to be
taking my family in this tunnel

and say,
"Look, I worked on this."

I think many tunnelers
like to think of themselves

as kind of the unsung heroes

because it's all underground.

NARRATOR:
Steve has been building tunnels
for over 25 years.

He started out as
a construction worker,

but now oversees the operation

of two giant tunnel boring
machines, called TBMs.

In all, there are eight of these
dirt-eating monsters.

Each one is 490 feet long
and weighs 1,000 tons.

The machines have been
boring away

for just over a year,
but now Steve's crew

is about to face
its toughest challenge yet.

The brand new tunnel
and ten new Crossrail stations

must connect into the existing
London Underground network.

This means
the tunnel boring machine

must drive dangerously close
to tunnels and other structures.

But only once
will they pass this close.

Engineers prepare to inch
one of the tunneling machines

through the tightest point
of the entire route,

known as
"The Eye of the Needle."

At the east end
of Oxford Street

lies London Underground's
Tottenham Court Road Station.

Crossrail's new tunnel
and station here

will link into two
existing Tube lines

called the Northern Line
and Central Line,

creating a Central London
super hub.

But digging tunnels here
is not easy.

Pipes, cables, and sewers
crowd the ground.

The Tube's busy Northern Line
platforms and two escalators

make the earth
extremely crowded.

The only option for Steve's team
is to drive

their tunneling machine
through the tightest of gaps,

33 inches above the live,
running Northern Line

and 14 inches
below the escalators.

It's the closest
any Crossrail tunnel will come

to the critical infrastructure
that keeps London ticking.

At the controls for
the tightest drive of them all

is engineer Ed Batty.

We've been in tricky spots
before,

but nothing where we've had
something below us and above us

in such a close proximity,
so yeah, it's a first for me.

My first job on a TBM,

and this is one year and
one month I've been down here.

The first six months was
a learning curve,

and now I know
what the crack is, basically.

NARRATOR:
Steve and the team
have a crucial meeting

with London Underground
to coordinate their next step:

how to avoid interrupting
Tube services.

MAN:
C'mon!

NARRATOR:
The tunnelers can't cause
any interruption

during the 48 hours
it will take their machine

to pass through
the Eye of the Needle.

The tunnel boring machine

is passing directly
over a platform tunnel,

so our customers
will be able to see

the impact of the tunnel boring
machine passing by.

For example, you could have
tiles falling off.

If we had customers
on the platform

who started seeing
a lot of fluid come in,

they might cause a panic.

If the worst comes to the worst,

we might have to evacuate
the station.

The only thing we've got
to bottom out

is what surveillance regime
we're going to have in place.

NARRATOR:
The team must keep a close eye
on the Tube platform

while the machine passes
overhead.

They will have just seconds
to halt the operation

should a crack appear.

PEARCE:
I suppose the real excitement,

if you like,
or the adrenaline will start

if there is an incident.

NARRATOR:
If all goes well here,
trains and people

passing through this station
won't miss a beat.

But if any of the other
construction sites

fall behind schedule,

the entire $23 billion project
could be derailed.

One site that could easily
become a problem

is the new Crossrail station
at Canary Wharf,

London's financial hub.

Here, workers are building
an utterly unique structure.

Since the 1980s, Canary Wharf
has been transformed

from a derelict
post-industrial wasteland

into the Wall Street of London,

home to many of Europe's
tallest buildings.

Over 100,000 people now work

in this booming
financial jungle,

so the area needs
better transportation links

to help get them all there.

At 1,050 feet long, Crossrail's
Canary Wharf Station is vast,

as long as three-and-a-half
football fields.

But because space around
the docks is at a premium,

they had to build it underwater.

To do so, they sank

an 840-foot-long watertight
concrete box

to form the station's walls.

Concrete pillars anchor it
into the dock bed.

They drained out more than 40
Olympic swimming pools of water,

then dug down to create

four additional floors
below water level

and built two floors above.

To transform this concrete box
into a station,

first they must build
the platforms,

then install the escalators.

But that's a walk in the park

compared to assembling
its intricate roof

from 1,500 timber beams

to house a public garden
open 24 hours a day.

This ambitious
thousand-ton canopy

will be built from specially
engineered timber beams

manufactured in Austria,

joined together using
860 steel connectors.

The wooden frame will be covered
by air-filled plastic panels,

enclosing the rooftop garden.

Overseeing the German
construction workers

who have six months to assemble
this giant 3-D puzzle...

NARRATOR:
...is Phil Duffy.

One or two of our lads
don't speak much English,

so it helps a little bit
to be able to speak a small bit.

(speaking German)

Okay, Prem,

up on one on the hoist,
up on one.

NARRATOR:
Phil's first milestone:

assemble the first arch
of the canopy.

If we don't have these
in the exact right position,

the timber elements won't fit.

Tiny bit down?

DUFFY:
Everything has to be

within the millimeter.

This is like the keystone.

The big crane will lift this in,

and hopefully then
it will slot in

to the exact right position.

If this aligns up, the whole
structure will follow through,

so this will be one
of the most critical lifts

of the whole thing.

Have you got a knife on that
little Swiss thing of yours?

It's for nails, but...

NARRATOR:
The first arch needs a keystone,
a two-ton timber unit

that will hold
the structure together.

RAY PALLETT:
We're just about to put
the center section in place

using the tower crane.

We'll get everybody else
out of the way,

and hopefully it will go well.

As you slew round, mate,

that should stay
same orientation.

Heads up, heads up!

Nice and steady,
inches at a time, please, mate,

nice and steady,
come down on your wire.

NARRATOR:
The keystone is in position,
but it's not a perfect fit.

Just trying to locate the bolts
on each corner.

It's literally millimeters out.

If we have an issue here at one
of these timber structures here,

it means it exaggerates
as you go along the building

and our connections
won't go in correctly.

For alignment,
they have to be perfect,

within maybe five mill.

NARRATOR:
So they apply
a bit of brute force.

PALLETT:
Hit it properly, Robin!

(laughs)

You can't beat the sledgehammer
at the end of the day.

(laughing)

Yeah, that's it.

Fairly chuffed, yeah.

Oh yeah, I think I should have
been a photographer.

What do you think?

If you stand back
and look at it,

you can see the whole arch

from one side
to the other side now,

which is perfect.

This is a massive structure,
like,

and when it goes to plan,
you can't be happier.

Looking more than good,
looking brilliant.

NARRATOR:
First milestone complete.

Okay!

NARRATOR:
They are on schedule for now,

but there are 1,300 pieces
of the puzzle to go.

And the station is only
five short miles

from Tottenham Court Road
and London's shopping district.

Already a large station,
it's growing further,

adding a network of underground
walkways and escalators

to connect it to Crossrail's
new tunnel and platform.

When completed, it will become
a greatly expanded gateway

to the shops above.

Just off the main thoroughfare

is the 335-year-old oasis
of Soho Square.

Crossrail is building
a new station

directly underneath
our feet here.

Our tunnel boring machine
is directly under this building

opposite us there.

NARRATOR:
Advancing on average
72 feet a day,

Crossrail's vast
tunnel boring machine

is closing in
on the Eye of the Needle.

The Tunnel Boring Machine,
or TBM,

has sharp cutters
in a huge rotating wheel

that scrape at the earth
like a drill.

Behind this cutter head is
an enclosed steel jacket

that holds the earth at bay

and creates a safe area
for the tunnelers.

Eight pre-cast segments
make up each ring,

and workers secure them
with bolts.

Once a ring is complete,

hydraulic rams push the machine
further forward into the ground.

Every five feet they advance

creates space
to build another ring.

In perfect conditions,

this digging demon can build
up to 45 rings a day,

leaving a water-tight,
tube-shaped train tunnel

in its wake.

ALDER:
We've got to pass
under a couple of buildings

before it gets
to the Eye of the Needle,

but before we get there,

obviously we've got to protect
the buildings.

We don't want to put
the table tennis table

out of level.

It's all part
of keeping London moving.

NARRATOR:
Digging directly under a city is
a delicate operation.

The loose ground
around freshly-dug tunnels

could settle unevenly,

potentially tilting
and damaging buildings.

So Crossrail's engineers use
a network of lasers and targets,

capable of registering
even a millimeter of movement

in any of the buildings.

ALDER:
If you look closely
on the buildings,

you can see lines
of these prisms

that are all across the facades.

On the far corner there

on the brackets
away from the building,

you can see an automatic station
up on the end there.

It will know where these prisms
are supposed to be,

it'll turn the instrument

to see where it last read
the prism from,

and then it will take the shot
that will give it

the exact location of the prism.

You'll see it rotating
round now,

working its way around,

and then sending all that data
back to the control room

so we know where all these
prisms are in real time.

NARRATOR:
Data from thousands of targets
installed across Central London

flows back to Tunnel Control.

Here, Simon Leavy specializes
in the analysis of this data,

picking up the slightest change
in ground level.

If the ground moves
either up or down,

we can tell from these graphs.

The nodes on the points
are blue,

so that means they're not
in any trigger area,

but if they go to a green,

it's a green alert,
amber and red.

NARRATOR:
Robot trackers keep an eye

on some of the oldest buildings
in London 24 hours a day.

Among them is one of
the most celebrated structures

next to Oxford Street,
in historic Soho Square:

the mid-18th century charity
and chapel

House of St. Barnabas.

MAN:
This is the plasterwork
installed in 1754.

It's a classic piece
of Rococo work.

The main hall

and the Silk Room next door

together constitute
the last complete set

of Rococo plasterwork in London.

NARRATOR:
This building is
under constant surveillance.

A steel frame
stands ready to catch

the 260-year-old staircase,
should it collapse.

The House of St. Barnabas
is bristling with instruments.

But despite steps taken

to support its stairway
and protect its pillars,

there's still a risk.

As workers dig
beneath Soho Square...

...the excavations are
disturbing the ground.

LEAVY:
In Soho Square now,
we have some amber triggers

on the leveling points.

It's not to do
with the TBM;

it's the new ticket hall.

They're actually excavating
fairly deep in that area.

NARRATOR:
Sensors on the House
of St. Barnabas

have triggered alerts.

It looks like cracks
in the rare plasterwork

are getting worse.

The corner behind me

has been gently moving
towards the square.

And we are watching the cracks

that are forming
in the plasterwork.

Now, we don't want to be panicky
about this,

but you have to keep an eye
on what's going on.

The main thing is to try
to ensure that

it all stays up there.

NARRATOR:
Tunnels beneath Soho put these
historic buildings at risk,

but the stakes are even higher
to the east,

where another team is digging
below the River Thames

at Custom House.

The train tunnels for Crossrail

need to pass
under the Royal Docks here.

In their Victorian heyday,

these were some of the largest
docks in the world.

And today,
they include London's

largest exhibition space:
The Excel Center.

The new Crossrail station

will make it easier and faster
to get here,

as well as
to London City Airport.

Much of the old
Victorian infrastructure

remains in place today,
including the Connaught Tunnel

that runs
underneath the water here.

Linda Miller,

an American engineer,
heads a team that is attempting

to rebuild this old tunnel

to make it suitable
for modern high-speed trains.

The mission
for the Connaught Tunnel team

is to turn a 135-year-old

beautiful piece
of Victorian architecture

to a state-of-the-art
modern tunnel.

NARRATOR:
The existing tunnel is too small

for Crossrail's trains
to squeeze through.

MILLER:
Well, I've been
on some very exciting jobs.

I've been lucky enough to build
a new space launch complex

at Cape Canaveral, Florida,

and do tunnels
in other beautiful cities,

but I reckon this is
my favorite job yet.

I love the idea
that we're bringing

beautiful old heritage railroad
back to life.

NARRATOR:
The Connaught Tunnel was built
in 1878.

Steam trains
once ran through here,

shuttling passengers
back and forth

to a ferry terminal.

MILLER:
You may just see
the old coke deposits

and memories of the steam trains
left above there,

but actually, what I see

is a tunnel that's
in cracking good condition,

fantastically well built,
you know, really built to last.

NARRATOR:
Dismantling and rebuilding
this robust underwater tunnel

will require a complete
rethinking of the structure.

For half of its length,
the Connaught tunnel

is a single tunnel
with two sets of tracks.

But not in the center
under the docks,

where it splits into two.

Linda's team must completely
rebuild this section,

creating a single taller,
deeper, and wider tunnel

big enough for two
Crossrail trains.

MILLER:
The first job then

is to start to deepen
this tunnel,

and you can see
that's just what we've done,

cutting away
and uncovering bricks

that haven't seen the light
in 130 years.

NARRATOR:
Linda's team must also remove
the steel rings

that Victorian engineers used
to form arches,

reinforcing
the tunnel roof here.

But a survey has revealed

that there is a problem
with this plan.

MILLER:
It was always assumed

that we could cut
these cast steel rings out

and replace them with rings
that were slightly larger

and that
that would all be fine

because we had a really good
level of cover

above the crown
of this old tunnel.

So it was shock and dismay
after we had our first divers

clear away quite a lot of silt

that was at the bottom
of the docks

and do a proper survey

and find that actually,
we have no cover at all.

NARRATOR:
That means that
the bottom of the dock

is perilously close
to the steel rings.

The current plan
to enlarge the tunnel

could lead to deadly
consequences.

MILLER:
The word we were
worried about is,

"Oh, my gosh, as we try
and cut these rings off

"of the crown of this roof
and that much water is above us,

catastrophic inundation,"

or the sluicing in,
uncontrolled sluicing in

of the Royal Docks
into this tunnel

became quite the real...
well, terror, really.

NARRATOR:
With little or no soil

separating the tunnel
from the water above,

removing the steel rings could
cause a catastrophic breach.

The only way
to expand the tunnel safely

is to seal off the passage
with giant steel barriers,

drain the water,

and rebuild the tunnel
top down

from inside this dry workspace.

But closing off the waterway
here could be a problem.

It's the only way river traffic
can pass to and from

the city's largest
exhibition space, Excel,

home to the annual
London Boat Show.

They can't start the process
until after the Boat Show,

when the road bridge can be
opened to allow the ships out.

And then they have
a narrow time window

of just six months
to complete the work.

If the passage
isn't open by then,

naval ships arriving
for the annual Defense Show

won't be able to reach the hall.

Time is also against
another team...

...three miles west
along the River Thames

in the busy new financial
district of Canary Wharf,

where Crossrail's
ambitious timber roof

is slowly taking shape.

But deep below the roof,

engineers are preparing
for a key milestone.

One of the eight
tunnel boring machines

is now nearing its first target.

It must break through

into Crossrail's vast new
Canary Wharf Station,

connecting the tunnel
with the platform space.

We're at the minus six level
of the Canary Wharf box,

and we're just waiting
on our first TBM

to pop its head through
for our first breakthrough.

This is our first breakthrough
on an existing structure,

so for us,
this is all about making sure

that the machine is
where it should be.

NARRATOR:
Canary Wharf Station is
a giant six-level box

with a garden, shops,

and restaurants
on the upper floors,

and the platforms
deep below ground.

The team here must drive
its tunnel boring machine

through the station's
concrete walls,

hitting a specially
designed target.

Crossrail's first breakthrough
is just a few inches away.

(applause)

(cheering)

NARRATOR:
Everyone is jubilant

as the machine hits its target
spot on.

Canary Wharf Station is now
connected to the new tunnel...

MAN:
One, two, three!

(cheering)

NARRATOR:
...putting the project
one step closer

to joining up with the hub
at Tottenham Court Road.

But in neighboring Soho Square,
the robot laser trackers

have detected a dangerous shift
in the ground,

threatening
the House of St. Barnabas

and putting its rare
Rococo decor in peril.

Engineers must stop the earth
from sinking

before it gets any worse.

Before tunneling began,

they dug 22 shafts
around Central London,

part of a subterranean system
to protect historic buildings.

Four of these shafts are
in Soho Square.

A spider's web of thin tubes
stretches out from each shaft.

Each tube has holes
every three feet.

Engineers send a narrow device
called a packer

to the spot
where the ground is settling.

The packer precision-injects
grout to fill up any voids,

lifting the earth back
to its original position,

protecting plasterwork,
preventing further cracks,

and keeping buildings safe.

MAN:
TAM number 46 then, yeah?

NARRATOR:
This shaft in the southeast
corner of Soho Square

is where grouters Lloyd and Tony
work to shore up the buildings.

LLOYD:
This is what we call a packer.

This rubber part here
will inflate.

That will form a seal to prevent
any grout coming back out.

90 meters is a long way
to push the packer,

but you take the rough
with the smooth, I think.

2-6-1-5!

Okay, 2-6-1-5.

NARRATOR:
Lloyd and Tony spend
up to 12 hours a day

down this shaft,
packing holes under Soho Square.

LLOYD:
Okay, that's depth.

inflate the packer.

That's ready to start pumping!

Yeah, pumping now.

I've been on the job for
about 16 months.

Tony's been with us for
about six months.

We generally tend
to stick together

as a team as well,
you know?

Yeah, we do come...

I mean, not too close,
obviously.

You don't want to get too close
in a place like this.

You get used to talking
to yourself,

but apart from that,
it's all right.

13-3-0-7-5!

Okay, up on the reel!

Whoa!

Welcome to the House of
St. Barnabas periodic meeting.

NARRATOR:
In order to keep
these historic buildings safe,

the Crossrail team
meets once a month

to analyze
the laser leveling data.

WOMAN:
And then the summary sheet

won't have any triggers
unless we get real movements.

NARRATOR:
They'll keep a close eye
on the House of St. Barnabas

and its Rococo plasterwork.

SCOTT:
The charming lady here
has survived

to keep us entertained
in the 21st century

and I hope for many more.

NARRATOR:
Finding a way to protect
historic buildings above ground

has been tough,
but a few miles away,

engineer Linda Miller struggles

with a potentially
disastrous situation.

She needs to expand
a 19th-century tunnel

running beneath the docks
next to the River Thames.

But the lack of headroom
has created a huge problem.

Now she's racing to find a way
to do the job

without causing a flood.

Faced with the reality

that she will first need
to drain the channel...

MILLER:
Thank you very much.

How exciting!

NARRATOR:
...Linda decides to read up
on the tunnel's history.

Now, this was the later stamp...

The original drawings,
135-year-old drawings there.

DAVID WILDE:
We've been presented
with the same problems

as the original construction,
basically.

A lot of it's to do with water

and how you actually build
something

with all the water around it.

NARRATOR:
She discovers that her plan
actually mirrors the techniques

used by the engineers
who originally built it.

MILLER:
"Existing dam."

See, that's history
repeating itself there.

Instead of tunneling
underneath the ground,

they've actually excavated
around the profile

and then installed the tunnel
in there.

So they've built it from
the top downwards, effectively.

MILLER:
Looking at the two twin-walled
cofferdams standing there

with "1872," "1874" written
in the corner of the drawings,

I think it was meant to be.

NARRATOR:
Finally, the London Boat Show
is over.

As the last luxury yachts
cruise out of the docks,

a narrow window of opportunity
opens for Linda's team.

They can now close the passage
directly above the tunnel

and drain it.

But they still don't have
the luxury of time.

They will have
to reopen it again

in time for navy ships
to get to the Defense Show

in just six months.

MILLER:
We'll try and quickly
get in here,

do open heart surgery

on this tunnel from the top,
rebuild it into a larger tunnel,

and get out of here by the time
the Defense Show comes.

It's hard work.

NARRATOR:
The last of the water is drained
from the dock,

exposing the 137-year-old roof
of the Connaught Tunnel.

PAUL OSBORNE:
We've got lots of workfronts
going on,

so we're working in the tunnel,
working in the dock,

we're all a team, basically,

working together
trying to achieve one goal.

NARRATOR:
The team must complete
a laundry list of challenges

in a very short time.

First task:

remove the steel rings
lining the twin tunnel section.

What you're able to see
quite clearly here,

now that the docks are empty,

you can see
the cast steel barrel.

The Crossrail tunnel is going
to be wider and rectangular

and fit its haunches
within the old tunnel.

NARRATOR:
Carefully, the team
removes the rings

without triggering a collapse.

But as they cut the steel away
in this corner,

they reveal a completely
unexpected brick arch behind.

That's a problem.

NARRATOR:
The new tunnel is supposed
to fit inside this arch,

but there's not enough clearance
for the new tunnel to fit in.

That's got to be removed.

NARRATOR:
They can't just remove
the brick arch

behind the steel rings

because it could be supporting
the docks above.

MILLER:
You're not going to be able
to take a section out of this

and still be able to hold on
to your arching effect.

Pretty unlikely.

Unlikely.

Is it the same
on the other side?

Yeah, but we don't know
how far.

All the rings they've
taken out so far,

we've got the reduced dimension.

All right.

Yeah, this is yet another time

when this tunnel
shows us new mysteries.

This job actually started
construction a year ahead

of when everyone said
that it needed to,

and it was because
a predecessor of mine said,

"It's going to be
a bucket of spiders."

And oh, my goodness,
have we used every bit of that,

and now we're staring
at the end date

that we never thought that we
would need to be worried about.

NARRATOR:
Linda and the team are already
facing a very tight deadline.

They can't afford
this new delay.

And they quickly discover
that the brickwork

is unusually tough.

MILLER:
The mortar between them

is 100% full.

There's no gaps here at all.

It's a fantastic,
fantastic job.

And then the 135 years of earth
pressure and water against it

has sealed it up
to where it's behaving

more like stainless steel
than it is brick and mortar.

NARRATOR:
The strong mortar is now causing
the latest problem for the team.

They can't get the bricks out
quickly enough.

OSBOURNE:
Just over a third
of the way to go.

It's quite slow going,
this brickwork.

You know I've seen brickwork
like this taken down,

and all you normally need to do

is have a couple of stabs
at the mortar

and a whole brick layer
goes off;

couple more stabs at the mortar,
the next layer goes off.

I know the men are taking
a short break here now,

but hand-breaking out
this 130-year-old brick

is just, well, hard work.

It's going to take a while.

I know they're working it
night and day,

I know they've got
extra crews in,

but there's not much time.

Here we are in the last throes
of the last couple of weeks

before we put the water back in.

We couldn't be throwing
more into it than this.

NARRATOR:
Linda's team works
around the clock

to remove the protruding arch
inside the Connaught Tunnel

and build a new roof
of steel and concrete

before they must re-flood
the channel

in the next 24 hours.

The final push pays off

as water streams back
into the area.

Linda and the team
have completed the tunnel

just in the nick of time.

WOMAN:
I can't believe you can see
all the way through!

No one's ever gonna have
been able to see that

all the way through.

MILLER:
Doesn't it look fantastic?

I know, it's mad!

I can't believe
it's finally done.

Feels so good.

Like, we're directly
below the docks right now

and you wouldn't know.

I know, below meters
of water there above us.

My gosh, we were working
like dogs, weren't we, 24/7?

It couldn't have been closer,
it couldn't have been closer.

WOMAN:
We've done it.

NARRATOR:
With the tunnel complete,
the dock can reopen,

allowing the military ships
to pass through.

The Excel's Defense Show
can go ahead on schedule.

This is the new Connaught Tunnel
for the next 120 years.

So you need to get
out of the way here

because trains are gonna start
coming through.

NARRATOR:
While this old tunnel has been
given a new lease of life,

at Tottenham Court Road,
a brand new tunnel

will soon squeeze through
the congested earth here.

The thousand-ton
tunnel-building monster

is finally entering
the Eye of the Needle.

Welcome, everyone,
to Sunday morning the 8th.

NARRATOR:
This is the day Steve's team
has been working towards.

That's where we are
at the moment,

just touching the side
of Charing Cross Road.

PARKER:
We're under the site
of the old Astoria Theatre,

aren't we, Willie?

ARCHIBALD:
Yep.

NARRATOR:
Today, the tunnel-boring machine

will reach the narrowest point
of its route across London.

MAN:
So the crossing starts

on back shift this afternoon,

and I think we're going
to be there, yeah.

Today is the critical day.

It's the start of passing
over the Northern Line,

and so this is
the critical point,

the culmination of a lot of work
over the last couple of months.

So people getting off the train
in the next hour or so

will not realize that
above their head

is a 900-ton,
7.1 meter-diameter

tunneling machine.

NARRATOR:
It's vital the close encounter
doesn't cause water or concrete

to fall onto the Tube platform
below, which could spark panic.

General comment is to say,

"Be aware of proximity
of LU assets."

MAN:
I mean, I would like Ed
to keep an eye on the belt.

Yeah, just extra vigilance.

So over the next 20 rings,

we're directly above
the Northern Line platform.

The Eye of the Needle.

We're just about to go
through it.

(phone ringing)

Hello?

Hello, Ed.

Hi, Steve, how you doing?

We've got one more ring to go

before the cutter head
gets in line with the angle

of the Northbound Line.

Tim Morrison of LU said
he was down this morning,

he was there, and he said

he could hear the TBM
and hear the miners.

(faint drilling noises)

BATTY:
We're that close,

so you can actually hear
what we're doing here.

PARKER:
Yes, he could hear,

but that with no trains running.

Our one concern is that there
are cracks within London clay,

some of the water could ease out

and find the simplest path
of travel,

which could be
the big platform tunnel.

BATTY:
The TBM cutter head

is now directly above

the Northern Line
northbound station platform,

so about 850 millimeters
below my feet

is the crown of their tunnel,
so not a big distance at all.

You see where there's
a blockwork wall here,

just behind the tiled edge?

That is pretty much
the center line

where the tunneling machine

is actually
crossing this structure.

NARRATOR:
With the tunneling machine
less than three feet above,

the pressure on the Northern
Line platform tunnel

will be immense.

The team is worried
about lubricating fluid

pumped into the earth
ahead of the machine

being forced through the wall
into the platform.

MORRISON:
Sam is one of the guys

who's been based down
on the platform.

He's specifically looking
for any fluid ingress

from the tunneling machine,
because that is something

that we are concerned
as a possibility.

SAM:
The tunneling machine
at the moment

is quite literally
above the tunnel crown.

There is that apprehension

because there is a small risk
that we could see some ingress,

and so I guess that makes it
more exciting.

NARRATOR:
With the tunneling machine

now threading
through the Eye of the Needle,

the team must continue their
vigil throughout the night.

As London sleeps...

(whirring)

...the 490-foot-long
earth-eating giant

continues its relentless drive.

With every passing moment,
the cutter head of the machine

draws ever closer
to the Northern Line

and its escalators.

Willie, got an update
where we are?

Yep, they're building 3024
just now.

NARRATOR:
Finally, the team and machine

squeak through the tightest spot
with only inches to spare.

Yep, okay!

NARRATOR:
A complete success--

no terrified passengers,
no evacuated platforms.

It's time to breathe again.

PARKER:
We've passed
over two platform tunnels

with a 900-ton
tunneling machine.

That's even a first,
I think.

MORRISON:
Yes, it is, yeah.

Cheers.

BATTY:
The lads have been working
down here really hard,

and so have the guys
up in the control room.

A big relief.

I'm chuffed that
we've done it so well

and we've had such good results.

We've done it, yeah,
got through the tricky spot.

PARKER:
The trains have kept running.

Passengers haven't known that
we've been there.

It's been a great achievement,

and I'm glad to be part
of that team.

NARRATOR:
The team leaves
a perfectly formed Tube tunnel

in their wake,

gradually closing the distance

to the new financial heart
in East London.

Here at Crossrail's
Canary Wharf Station,

Phil's team is locking
the last beams into place.

DUFFY:
Everything's going perfect,
thank God.

Everything is good.

It's the biggest project
that we've done.

Something to be proud of,
I suppose.

NARRATOR:
Final piece of the puzzle:

780 inflatable panels
known as cushions

that will fill the gaps

and cover most
of the rooftop garden.

Installing them requires
a head for heights,

so they've assembled
a crew of builders

with a special talent.

MAN:
They're rock climbers
and mountain climbers,

so they're used to heights,
and yes, a very skilled trade.

Basically, they're just
unwrapping the cushion now.

It comes all folded up,
they unfold it.

They have to put
aluminum sections

which run down the edge.

Then they'll connect it
into the system,

connect the air pipes,
and blow it up.

Sounds simple;
little bit more difficult.

NARRATOR:
Fitting the first cushion
on the lower outside edge

will be a real test.

Below is a 65-foot drop.

Because we're installing
the cushion

almost on the vertical face,

there is no area
for a safety net.

This is the...

The most susceptible point
of the installation

is when it's opened.

If the wind catches it, then
that's the worst-case scenario.

Once it's got the rails on it
and it's attached, it's secure.

They're now fitting
the air inlet,

so any moment now, you'll see
the cushion inflating.

It is actually starting
to inflate now.

One done, about 750 to go.

I'm a happy bunny.

MAN:
It's growing, you know?

It's getting more beautiful
every day.

NARRATOR:
130 feet below the roof,

the station's 790-foot-long
platforms are being fitted out.

And the final timber
slots into place on the roof.

All our timbers are fitted,
everything is done now.

Someone else's problem now.

I'm out of here,
back to Ireland.

(humming cheerful tune)

NARRATOR:
So far, Crossrail's
10,000 employees

have put in a hundred million
working hours...

(cheering)

...poured over 88 million
cubic feet of concrete,

and laid over 200,000
tunnel segments.

In 2018, the ticket halls
will open

and the escalators
start running.

Before then,
the team must lay the tracks

and build the trains.

London's population

is set to pass
nine million people in 2018,

and they will have
a new $23 billion rail line

to keep them on the move.

This NOVA program is available
on DVD and Blu-ray.

NOVA is also available
for download on iTunes.