Original subtitles

♪

Narrator: In los angeles...

Hey, pull it again, tony!

...This elite team of engineers

Is embarking on an epic endeavor.

They're building three brand-new subway lines

Through the heart of the city.

It is the biggest civil-engineering project

To ever take place in tinseltown.

Oh, yeah.

[ indistinct conversation ]

It's going to be transformative when it opens.

Hey!

Narrator: To build this colossus,

The team must battle dangerous earthquakes...

[ rumbling ]

I think it's a crazy place to build a tunnel.

Narrator: ...Deadly pockets of gas...

Carbon monoxide -- it can kill you.

Narrator: ...And a labyrinth of underground obstacles.

That was like going through a minefield.

[ beeping ]

Oh.

Hold on a second, danny.

I'm not sure why that's there.

Narrator: This subterranean earthquake-proof railway ranks

In a league of ambitious new engineering wonders

That are bigger, faster, taller, and more advanced

Than anything ever constructed before.

This is the inside story of the extraordinary challenge

Of building these giants.

♪

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

Captions paid for by discovery communications

♪

Los angeles...

Home of hollywood...

♪

...Sunshine...

♪

...And some of the worst traffic on the planet.

♪

The city's aging highways

Are pushed beyond their limits.

[ horns honking ]

♪

The average angelino spends more than 120 hours

Stuck in traffic every year.

[ horns honking ]

I used to commute here,

And it would take 2 hours there, 2 hours back,

And it's 4 hours of my day just gone.

Woman: Like, even at 5:00 in the morning,

There's commuter traffic. It's stop-and-go.

Narrator: To overcome this problem,

The citizens of los angeles

Are funding a new multibillion-dollar expansion

Of the city's existing metro network.

The new subway lines will connect the city

Like never before

To relieve the pressure on its overburdened highways.

♪

On the south side of the city, a brand-new 8-1/2-mile line

Will whisk passengers from lax airport

Through eight new stations into central l.A.

♪

Further north, engineers will dig 9 miles of tunnels

And construct 7 new stations

To connect l.A.'s westside and beverly hills.

♪

Beneath the skyscrapers of downtown, a new line

And three new stations will form a crucial link

Between the city's existing but unconnected subway lines.

This ambitious project

Should reduce congestion on l.A.'s roadways

And increase the metro's usage by 30 million people a year,

Radically transforming travel in l.A.

♪

Overseeing this massive project

Is tunneling expert bryan pennington.

[ speaking indistinctly ]

It will change the face of the city.

All underground systems in a city are complicated.

This area has probably got just about

Every complication you could imagine.

Narrator: In this dense urban landscape,

Engineers must build most of the new railway underground,

But the terrain below l.A. Is treacherous.

It's filled with deadly gas, earthquake fault lines,

And a maze of skyscraper foundations.

This is the plan.

♪

To link lax to central l.A.,

The team will build more than 8 1/2 miles of new track.

Nearly 7 miles will be aboveground,

Running alongside roadways and over six new bridges.

The other 2 miles will run underground.

To the north of the city, huge tunneling machines

Will dig two new parallel tunnels 16 feet apart.

These digging demons will plow through 70 feet of earth

Every day,

Leaving a superstrong tunnel behind.

Beneath downtown l.A.,

Engineers need to build a crucial connection

Between the existing lines.

To do this, they'll manually dig out 1,300 feet of new tunnel

Through a tangle of skyscraper foundations,

Removing thousands of tons of earth

From under one of the city's busiest streets.

Taking 15 years and costing more than $11 billion,

The project will bring l.A. Together like never before.

♪

Work begins in 2014.

The team spend years digging access tunnels...

♪

...Preparing station sites...

♪

...And clearing routes for service lines.

Now they face their toughest challenge yet --

The extension of the subterranean line

Right through the earthquake zones to the west of the city.

Clear!

To build it, engineers must use two huge tunnel-boring machines.

At the front, a 22-foot-diameter cutting head chews

Through the clay.

The cutterhead is turning and cutting the ground

Just like a cheese grater as it's propelling forward.

♪

Narrator: 32 powerful hydraulic rams

Slowly push the machine forwards.

[ men shouting ]

It stops moving every 5 feet so workers

Can install a new section of tunnel.

[ men shouting ]

♪

They're built of superstrong concrete segments

Locked together in a solid ring.

This should protect passengers

From the ever-present threat of earthquakes.

Man: Oh.

These can cause massive damage to structures aboveground.

♪

But belowground, the tunnel simply moves with the earth

As it shakes,

Making it one of the safest places in the city.

Halsey: The segments will move with the ground.

I've been in a earthquake two times,

And both times, we didn't feel it.

Narrator: Earthquakes may not be keeping the team up at night,

But hidden within the ground is another invisible

And deadly threat...

[ bubbling ]

...Gas.

♪

Gas tester j.R.

Is one of the most important members of the team.

He monitors the tunnel for gas

At all times to keep the miners safe.

Some gases down here are poisonous.

Others, like methane, are explosive.

The miners need a way to keep gas outside of the tunnel.

♪

Without any protective measures,

Invisible gas would slowly seep into the tunnels

From hidden pockets within the l.A. Soil.

If a spark ignited the dangerous gas,

The results could be disastrous.

So to prevent it from ever entering into these tunnels,

Engineers build the walls out of impermeable concrete slabs.

To keep the joints airtight, they line up two layers

Of high-density rubber to form a seal.

Finally, they inject special liquid concrete

Behind every tunnel ring, stabilizing the ground around it

And locking the seals tightly together.

♪

Every time the cutterhead pushes forwards,

It's a race to construct the newest tunnel ring.

♪

They use a train to haul the precast concrete segments

Up to the work site.

Man: Full speed ahead!

Violet: These are all wedged together.

These gaskets line up.

It makes a pretty good seal.

This helps a lot with keeping the gas outside.

Narrator: To make these seals gas-tight,

They must line up the sections with millimeter precision.

The crane operator picks them up one by one

And maneuvers them into position...

Man: Whoa!

...Guided by the watchful eye of bolt fitter lalo.

14! 11! 10!

Lalo: I'm his eyes.

I tell him if he's going to hit something,

If something's in the way, "stop," "go."

He has to listen to me at end of the day.

3...2...1!

Good! Good.

Narrator: Once each section is aligned...

Release!

...Lalo bolts it into place.

Good!

Lalo: You have to know what you're doing,

And if not, you will definitely get hurt.

Narrator: The team fits this final ring segment,

And another 5 feet of tunnel is complete.

Good!

With the ring in place, the miners can breathe more easily.

Good! Good!

Narrator: But as the tunnel-boring machine advances,

It leaves a void in the soft soil outside the concrete rings.

If this collapses, it would be a disaster

For the busy streets above,

So the team needs to work fast to stabilize the ground.

A.J.: It's watching all these numbers.

If something happens, it's like that.

♪

Narrator: Beneath the busy streets of los angeles,

A team of engineers is building a massive extension

To the city's underground metro network.

Whoa! Good!

Narrator: On the west side of the city,

Miners have tunneled almost 2 miles of the brand-new subway

Connecting beverly hills to downtown,

But as their digging machine moves forward,

It leaves a void around the outside of the tunnel.

Go! To prevent a collapse,

The miners need to stabilize the soft earth

With a special liquid cement called grout.

I'm basically the grout guy.

And that's it. Cut. Cut.

♪

The grout flows into the earth,

Filling up any gaps and reinforcing the ground.

Boom. See? Stopped on its own.

Grouted to pressure on that one.

Narrator: This quick-setting concrete

Should support the tunnel

And stop the city above from sinking,

But they are right below some of l.A.'s

Most densely populated streets.

The team can't take any chances.

So up at street level, engineers install superaccurate sensors

That detect the slightest movement of the ground.

The system is under the watchful eye of geologist peter mcdonald.

Mcdonald: There are hundreds of instruments

And settlement points running up and down wilshire boulevard.

The tunnel-boring machine will come this way

Right under our feet.

Narrator: The metro's new tunnels will lie just 50 feet

Below the foundations of l.A.,

So engineers must closely monitor any movement,

Looking out for signs of dangerous subsidence.

Aboveground, they install an advanced network

Of lasers and prisms.

The lasers fire a beam which the prisms reflect back

To measure distances down to 1/1,000 millimeter.

The measurements indicate if the tunnel building

Is causing the structures above to move.

Belowground, they bury over 1,000 motion detectors

Beneath the streets

To monitor tiny shifts in the soil in real time.

If any of their measurements suddenly change,

Engineers can alert the team beneath to stop tunneling

Before any damage is done.

♪

Installing such a vast network of sensors across l.A.

Is a major challenge.

Today, the team is positioning one

Of the highly sensitive underground motion detectors.

The sensormate we're installing acts as an early warning system

To detect ground movement caused by tunneling.

♪

Narrator: A massive rig

Slowly cuts a borehole into the street...

♪

...Drilling 70 feet down into the ground.

[ man shouting indistinctly ]

♪

[ indistinct conversation ]

♪

They place the new sensor,

Which will measure ground movements

As small as 1/1,000 millimeter.

Looks good.

The slightest slip triggers an automatic warning

That alerts miners to stop digging

Until they have stabilized the ground.

Mcdonald: Most of these instruments are automated,

Reading at a 15-minute interval.

I can pull up information for just about every sensor

We have on the site.

Narrator: This new motion detector

Links up with peter's extensive network of high-tech sensors,

Which stand sentry over the street...

Lalo: Clear!

...As the tunneling machines rumble on below.

Good! Give me another retract on below!

While work continues on the west side of the city,

At the center of downtown l.A., another team of workers

Is battling to build a new stretch of metro line

Right below the high-rise business district.

This 1.9-mile-long line is called the regional connector

And will make a huge difference to l.A.'s residents.

Currently in downtown l.A., four separate railways

Take angelinos to long beach, east l.A.,

And the rest of the country through union station,

But they aren't linked together.

It's impossible to travel across downtown

Without changing trains several times.

The regional connector will change this.

Three additional stations will bring new areas

Of the city into the network, and 1.9 miles of new tunnels

Will bridge the gap between pre-existing rail lines,

Enabling passengers to travel across the city

From the mountains to the pacific

Without ever leaving their seat.

♪

To construct the station buildings for the new line,

Workers dig out three enormous trenches.

The deepest, for the station at bunker hill,

Dives more than 135 feet down into the ground.

♪

To connect these stations, a tunnel-boring machine

Carves out 2 miles of subway under l.A.'s busy center.

♪

Today, there's just one final stretch to excavate,

But it's the toughest of all.

We're dealing with some of the most challenging areas

To work within in los angeles.

♪

Narrator: In los angeles,

Engineers are constructing a brand-new subway line

Beneath the high-rises in the heart of the city.

A tunnel-boring machine

Has quickly carved out nearly 2 miles of tunnel,

But now work has slowed to a crawl.

Overseeing this phase of the project

Is construction manager michael harrington.

Harrington: The public probably has no idea what is going on

Underneath their feet as they're walking up above us.

Narrator: Michael faces a major problem.

It's impossible to use the fast

And efficient tunnel-boring machines

To dig out this final 1,300-foot stretch,

Thanks to the soaring skyscrapers aboveground.

Harrington: When those high-rise buildings were built,

Their foundations came right into this excavation.

We couldn't bring the tbm down here

Because there was just too much risk of it

Striking one of these elements and getting stuck.

Narrator: The ground beneath the financial district

Is a tangled maze of foundations,

Utility pipes, and cables.

These dangerous hidden obstacles make it impossible

To use a tunneling machine to excavate the subway,

So the team must dig manually.

They start by excavating a narrow access trench in the road

And then carefully hollow out the tunnels from there.

As the tunnel grows, a chain of earth movers shifts

The waste material out through the tunnel entrance.

Then things get even tougher.

Once they reach the far end of the new tunnel,

Demolition experts must carefully break

Through a 2-foot-thick concrete wall

Into the existing metro network at 7th street station.

♪

The team of digger and bulldozer operators

Painstakingly excavates nearly 3 million cubic feet of dirt,

Dodging the many obstacles.

Some of the work around the utilities is being done

With a shovel.

Narrator: Earth movers shuttle buckets of soil

To the tiny access opening, and a single digger scoops

It out into the waiting dump trucks through the narrow hole.

Harrington: 10-4!

I equate it to the old-school passing the bucket

From one person to another.

We're talking thousands of moves,

And you have thousands of hours of labor

Just to remove the dirt.

Narrator: The tunnel grows steadily longer

Towards the existing station at 7th street.

Here a wrecking crew will break through to connect

The railway to the existing lines.

For the new line to have any chance of opening on time,

It's vital that the station is connected soon.

The slow excavation pushes the schedule down to the wire.

And we're coming up against a hard deadline here.

Narrator: The diggers work around the clock.

♪

After 2 1/2 years of work,

They finally clear out this cathedral-like space

Just in time for the wall to come down.

Harrington: Today is a really big day for metro.

Today is the day we start punching through,

Connecting our project to the existing system.

♪

Narrator: Now workers have to break through a wall

Into 7th street station

With trains still running just a few feet away.

We do have an open station on the other side,

So we have to keep dust and debris from entering that area.

Narrator: Conventional cutting tools won't work here,

So the team plans to use this very special wire saw.

♪

This is the wire that we're cutting with.

It's just a braided wire that's got these manufactured

Diamond segments about every inch.

Pulling this through the concrete actually cuts it.

Narrator: Michael's team threads the abrasive steel wires

Through holes drilled into the 2-foot-thick concrete walls.

Man: Good!

A machine pulls these wire loops through the wall at high speed,

Slicing it into a series of blocks

That they will carefully remove one by one.

This is precise engineering surgery.

We want to very carefully surgically remove

This section of the wall.

We don't want to use anything that could

Potentially damage the existing structure.

Narrator: But this meticulous process is painstakingly slow,

And it isn't long before they fall behind schedule.

To make matters worse, suddenly the wire jams in the concrete.

Carillo: Up or down?

If the team can't wrestle it free soon,

They could miss their deadline

And face costly delays.

♪

Narrator: In los angeles,

Engineers are constructing a brand-new subway line

Beneath the high-rises in the heart of the city.

♪

It's taken more than 2 years to build this tunnel

That connects four sections

Of the already operating metro network,

But now work to punch through this 2-foot-thick concrete wall

To connect the new line with the existing metro network

Has ground to a halt.

The diamond-coated wire saw...

Tony: More?! ...Is stuck.

Feed it backwards!

The only way to free the wire is to enlarge the hole...

♪

...And haul it out by hand.

♪

With a final pull, they get the saw working again.

Man: Yeah, we're moving.

No!

Now the team is playing catch-up.

Looks like we're going to have to work a lot of overtime.

For three grueling weeks,

The cutting team works around the clock.

Here we go. Here we go.

[ shouts indistinctly ]

They make 14 incisions in the wall,

Slicing it into a grid of 12 huge blocks.

♪

The final task is to take them out one by one

And break through to the station beyond.

We are now removing the blocks that have been saw-cut

Into pieces over the last several days.

Workers bore holes into the center of each block

And attach cables to haul them out of the wall.

Man: They look good. They look good.

Narrator: With a careful nudge,

The first block starts to inch out.

It's a tense moment for the crew.

This block weighs over 7,000 pounds.

If they don't pull it out square, it could cause the wall

To collapse and damage the operational station behind.

[ man speaking indistinctly ]

Narrator: The first block slides free...

And the wall remains intact.

[ horn honks ]

[ indistinct conversation, laughter ]

♪

The team works from the top of the wall

Down to haul the rest of the blocks out.

♪

And piece by piece, an opening appears.

The new tunnel finally connects to the existing station

On the other side

And the many miles of metro rail beyond.

Harrington: We are now connecting the project

To the existing metro system for the first time.

♪

♪

Narrator: All across the city,

The massive excavations for the new metro lines

And stations have removed millions of tons of earth.

This is a once-in-a-generation opportunity

For one of the team's more specialized members --

Project paleontologist ashley leger.

Most of the earth beneath los angeles

Is a mix of clay, sand, and tar,

The ancient bed of the pacific ocean.

Huge numbers of fossils are preserved inside.

♪

Ashley and her team keep a close eye on the excavation here.

They've discovered a remarkable number of fossils

Hidden in the dirt.

♪

At her lab, ashley's team cleans and catalogs all their finds.

This is the giant-ground-sloth skull.

♪

This is andy.

This is the long-horned bison horn core.

This animal was huge.

We're not just finding broken pieces.

We're finding big, complete, beautiful specimens.

My favorite is hayden, the mammoth skull.

Narrator: These remarkable fossils

Aren't just a time capsule of l.A.'s past.

They can even help the miners see into the future.

Leger: We can tell them that we know we've got to be getting close

To the marine layer,

So we can give them a heads up that,

"hey, here comes the beach sand, guys.

Excavation is about to change a lot."

♪

Narrator: While teams race to excavate the new railway tunnels,

Stations, and prehistoric monsters,

On the south side of the city,

A brand-new line is almost ready to open to the public.

The crenshaw line connects the airport to central l.A.

After three years' work, today engineers are testing it

By running trains on the railway for the very first time.

You want to go? Yeah, go.

If these tests reveal hidden issues

Embedded within their system,

They could delay the grand opening by many costly weeks.

Hold on a second, danny.

♪

♪

Narrator: In los angeles,

To ease the city's crippling traffic problems,

Engineers are building a multibillion-dollar expansion

Of the city's metro network.

After three years of work,

The crenshaw line that connects the airport to central l.A.

Is almost ready to open to the public.

Today, engineers plan to put it to the test.

They're gearing up to run trains on the railway

For the very first time.

[ man speaking indistinctly ]

I'll be operating between the crenshaw line

And the green line --

Make sure that we're getting all the signals we need out here.

Veteran driver danny mathison takes control

Of today's crucial test.

He needs to run his train

Just a few hundred yards backwards and forwards

Across this brand-new section of track.

It's where the new crenshaw line

Connects with the existing green line.

The pressure's on.

A problem today could reveal hidden issues

Embedded within their system.

I think we're in 3t.

To run properly, the metro network relies

On a series of electronic signals

Transferred through the track.

It's vital the trains pick up these signals

From the new sections of rail.

♪

You want to go? Yeah, go.

Here we go. [ bell clangs ]

♪

Danny slowly moves his train forward,

And the team puts the signaling system to the test...

♪

...Driving one way...

♪

...And then the other...

Through the short section of track...

Man: Good morning. 1015 is here.

Narrator: ...Checking signals one by one.

[ beep ]

It was a turn back at 8.

♪

[ beeping ] oh, no.

Hold on a second, danny.

They soon hit a problem.

Yeah, but we still have this -- wait, wait, wait, wait.

Yeah, go ahead. We still have that ues.

Some of the signals aren't passing through the new tracks

And into danny's cab.

Engineer steve sheroke is determined

To identify the problem.

Okay. Let's try to go again.

♪

Nothing? Nothing. It's not moving.

Okay. So, we should have a straight route.

Give me a second here.

After a few tests...

Here we go. ...He pinpoints the issue.

There are some glitches in the system

That are making the signals drop out.

The cab signal's intermittent. It's not stable and continuous.

It's fluctuating.

All righty.

We'll try something else.

[ sighs ]

With time running out on the test,

Steve tweaks the signal software...

Alright.

Got it.

Alright. There we go.

...And danny gives it one last try.

♪

Yep. There it is. Mm-hmm.

Success.

The signal system is up and running.

Another beautiful day in paradise. [ chuckles ]

Narrator: It's a huge relief for the crew...

That'll make so many people happy.

...And a massive step forward for the crenshaw line.

It won't be long before the first passengers

Ride trains through here.

You'll be able to get on with a surfboard,

Be able to board the train, and head west to the beach

And get off within walking distance of the pier

At santa monica.

♪

♪

Narrator: To the west of the city,

The tunnelers digging the line

Between beverly hills and downtown

Are reaching a critical milestone.

Level it! Level it!

After six months underground...

Clear!

...The massive tunnel-boring machine

Is set to break through and complete the subway.

Jonason: We've been planning this for 6 months.

We have just over 7 feet to go.

Narrator: In this complicated maneuver, the big question is,

Will it break through in the right spot?

♪

Narrator: In los angeles,

Engineers are overhauling

The city's public transport system

By building a multibillion-dollar expansion

Of the city's metro network.

To the west of the city,

Workers constructing the line from beverly hills to downtown

Hit a crucial milestone.

The first 2 miles of new tunnel is almost complete.

Jonason: We're somewhere between 6 and 8 feet out.

Narrator: For 6 months,

The 1,000-ton tunnel-boring machine

Has chewed through the ground

50 feet below wilshire boulevard,

Guided by the calculations of engineer josh jonason.

Jonason: We have just over 7 feet to go.

We've been planning this for 6 months.

Narrator: Now this 400-foot-long behemoth

Must break through a specially

Built target only inches bigger than itself.

This is how they'll do it.

As the digging machine begins its final approach,

Workers on the other side of the rock

Prepare for the breakthrough.

They install a reinforced steel ring

Exactly where the boring machine should come through the wall.

They seal this with a concrete cap

That will hold back the debris from the breakthrough.

♪

The ring the team has prepared

Is only a few inches larger than the cutting head.

Engineers must hit this target exactly,

Or they could damage the wall and cause costly delays.

♪

While josh and his team face an anxious wait...

Jonason: It's almost like you can hear the cutterhead.

Narrator: ...On the other side of the concrete wall,

The team is gearing up for breakthrough.

♪

In the driver's seat, scott halsey lines up

For the last few pushes.

Halsey: I'm trying to make this thing go as fast as possible

Without stalling the cutterhead or messing anything up.

[ chuckles ]

Narrator: As the tunneling machine chews through the soft ground,

It's down to scott to keep one eye on the dials

And one eye on the target.

Halsey: We have 6 inches of play around the machine,

So we got to make it pretty spot-on.

There's no sharp curves in this thing.

Narrator: If the machine is more than a few inches out of line,

It could bring down the whole wall.

I've got us at 374 plus 02.85,

So I've got us at 5 feet away right now.

[ man speaking indistinctly ]

The teams on either side of the wall

Stay in constant contact to check its position.

♪

The machine burrows another 5 feet closer to its goal.

Scott stops the steady forward pressure

Of the massive hydraulic rams

So the miners can place

The sections of the final tunnel ring.

♪

With only a few feet to go...

Got about 2 feet left.

...It all comes down to one last push.

♪

This is the critical moment

They've been working towards for six months.

♪

[ alarm blares ]

With a careful nudge...

The concrete cap buckles...

There she goes.

...And they finally break through.

Oh, yeah.

♪

There she is.

♪

[ chuckles ]

That might have been the prettiest hole-through

I ever saw.

Violet: [ laughs ]

♪

Narrator: After months underground,

The machine emerges from the darkness with perfect precision.

With this new tunnel,

L.A.'s subway system has grown by another 2 miles...

♪

...And the city's brand-new metro network

Is one massive step closer to completion.

[ laughs ]

Narrator: Los angeles's new world-class public transportation system

Stretches from the mountains to the ocean,

Easing the load on the city's maxed-out highways...

♪

Jonason: It's definitely something to be proud of

When you go back and look at how much work it took

To make that happen.

Narrator: ...And keeping the city running for generations to come.

Halsey: I'm going to be able to take my kids and grandkids someday,

And they're going to know that I helped build this tunnel.

♪