Original subtitles

NARRATOR: They're watching you.

More than 5,000 satellites circle the Earth.

Every day, they uncover new

mysterious phenomena that defy explanation.

From the skies,

the hunt for the lost Viking army.

I think this is where the kings were being buried.

NARRATOR: The lagoon of horrors.

This water is basically a poison stew.

NARRATOR: And the CIA

versus the super warriors of the ancient world.

You name it, they were prepared for it.

NARRATOR: Baffling phenomena, mysteries from space.

What on Earth are they?

[theme music playing]

Derbyshire,

a deeply historic county in the center of England.

200,000 years after humans first walked these lands,

Mark Horton has been drawn here

by a mystery revealed from the skies.

This is a fascinating image.

It's of a shape that I've never really seen before.

NARRATOR: An aerial laser scan of a patch of remote

forest has revealed groups of circular structures,

lost to history.

HYMEL: What we're looking at here

seem to be clusters of almost

what looks like pimples on the ground.

KOUROUNIS: There are so many lumps and bumps.

Looks like this countryside has got chicken pox.

NARRATOR: Elsewhere across the U.K.

are similar-shaped structures,

the earthen tombs of warriors and chieftains,

casualties from 5,000 years of this country's long,

bloody history.

Horton thinks these, too, are burial mounds,

but something about them doesn't make sense.

What's really exciting about this particular group

of mounds is that they're tightly packed.

I've never ever seen examples like

that anywhere in the British Isles.

NARRATOR: This arrangement could suggest that this patch of

forest was once a place of mass slaughter.

HYMEL: Because we're looking at so many mounds,

it could be the result of

a major battle, where they bury the bodies

near where they fell.

I think this is the -- the woodland.

It's massively impenetrable and thick,

with barbed wire and everything -- somebody...

clearly doesn't want anyone to get in here.

Hi, it's Mark here. Hiya.

Surrounded by...

NARRATOR: Horton learns that the mounds sit on

private land, and entry is strictly prohibited.

Are you saying that the public aren't allowed in here at all?

So frustrating.

But another contact does have some better news.

That's really interesting.

Can I come over and see them?

NARRATOR: Human remains have been discovered

near the site in the image.

Dr. Cat Jarman is analyzing them for clues.

These skulls are absolutely fantastic.

Where were they actually found?

These skulls here were all found in a mass grave

really close to the mounds.

There was almost 300 of them all together,

all jumbled up.

NARRATOR: Dr. Jarman's studies have revealed

the mass grave is a relic of

one of the bloodiest periods in England's history.

These skulls actually date to the Viking Age.

So the mounds I've seen on the image could be Viking.

I think that's very possible.

NARRATOR: The Vikings arrive in England in 793 AD, spurring

a wave of pillage and terror that lasts for over

two centuries.

And what Dr. Jarman's work has shown is that these remains

and the ones hidden in the woods

could be those of perhaps the most

feared Norsemen of all.

All the new scientific evidence is really very

strongly suggesting that this is the Great Heathen Army.

NARRATOR: The Great Heathen Army was a monstrous force

of Vikings who invaded England in 865 AD.

[men shouting]

Its arrival marks a dramatic escalation in

the decades of bloodshed that had preceded it.

In the beginning, the Vikings were primarily smash

and grab Raiders,

but in 865, that all changed.

We're talking thousands, and they had

the express goal of taking over England.

HYMEL: This army is organized, it has a single purpose.

They're not looking to pillage,

they're looking to conquer.

NARRATOR: At the time, England is ruled

by four separate kingdoms,

Northumbria, Mercia, East Anglia, and Wessex.

The ninth century Anglo-Saxon Chronicles describe how

the heathen warriors quickly conquer

two of these realms, slaying or subjugating

all who stand in their path.

We know that they were up

against some really strong Anglo-Saxon forces.

So we are talking about substantial

number of people moving through the landscape.

NARRATOR: The army is led by Ivar the Boneless,

son of the legendary Viking hero,

Ragnar Lodbrok and a warrior of

incredible cruelty and ferocity.

[man shouting]

It was a wave of terror in human form,

and there wasn't a thing you could do about it.

[men shouting]

NARRATOR: Historians believe the Heathen Army

contained around 10,000 warriors,

a force without parallel in Viking history.

Yet few traces of it have ever been found.

HYMEL: The Great Heathen Army,

it's steeped with mystery, because there's

no real physical evidence of its existence.

NARRATOR: However, near the site in the image,

Jarman has discovered possible evidence

of the army's presence,

pieces of Hnefatafl, a game

which its warriors reputedly played between battles.

Hnefatafl is a board game a bit like drafts or checkers.

So they're the smoking gun of the Great Heathen Army.

Absolutely -- wherever the army has been,

we are also finding these gaming pieces.

NARRATOR: Horton is convinced that the graves in

the image hold the remains of the Norse invaders.

The number buried there suggests that something

of great value to them must lie nearby.

The question is, why are the Vikings

coming here to the middle of England?

What would have attracted them to this place?

NARRATOR: Coming up,

into the Vikings chamber of secrets.

Once they captured this,

they've captured the soul of Saxon England.

NARRATOR: And terror from the skies.

[explosion blasts]

One wrong move at the wrong moment will get you dead.

NARRATOR: In Derbyshire, England, Mark Horton is on

the trail of the Great Heathen Army,

a force of some 10,000 Viking warriors who

rampaged across the country in the ninth century AD.

This was the army that successively defeated

each of the kingdoms of Anglo-Saxon England

and installed their own kings.

♪

NARRATOR: Aerial scans suggest that hundreds of

these legendary Norsemen lie buried in nearby woods.

The question, to me, is why did they

come here at all to this area in these midlands?

NARRATOR: Horton turns to 3D surveys, which

reveal the remains of ancient waterways

the Vikings used to plunder the area around the image.

There's one here which is really interesting,

because that comes

alongside what appears to be a small settlement or a village.

NARRATOR: Horton tracks the waterway from the mounds

to the settlement.

I can see the church.

This is actually beginning to make sense.

NARRATOR: In Viking-era England, churches take 10 percent of

the local population's annual earnings in taxes,

and they are filled with gold ornaments and valuables...

...sacred to the Christian Saxons,

but not to the pagan Vikings.

[men clamoring]

I can imagine the excitement of those Vikings

rowing up this river

and realizing that this was a treasure for the taking.

NARRATOR: Much of the church appears to have been

built after the arrival of the Great Heathen Army,

but not all.

Gosh, there's a little -- little passage

that takes us right underground.

NARRATOR: Horton finds himself in a 250-square-foot

subterranean chamber.

HORTON: This is an extraordinary space.

I think that this crypt must be Saxon,

and then the medieval church has been built on top.

NARRATOR: Historical records confirm that this crypt

was constructed in the 8th century AD,

meaning it is one of

the oldest Christian sites in the country.

What makes it such a target for the Heathen Army is that it

sits in the town of Repton,

the capital of Mercia,

the most powerful of the four main Anglo-Saxon kingdoms.

Mercia was a rich kingdom.

This is where the greatest concentration of power,

authority, and money rests, and the Vikings knew that.

NARRATOR: When the Great Heathen Army arrives in Mercia

in 867 AD, two of the kingdoms,

East Anglia and Northumbria, had already fallen to its swords.

To complete their conquest, the Vikings need Mercia's

Christian riches to bolster their war chest.

Yet as Horton explores the crypt,

he finds clues that it contains something of much

greater value to the Vikings than gold and silver.

You've got these little recesses,

one, two, and three recesses.

That reminds me of places where coffins,

or sarcophagi, would have been placed.

NARRATOR: The size of the crypt and its ornate decoration

suggests that it was once the resting place

of the most powerful people in the kingdom.

I think that this isn't just a crypt.

This is a royal crypt.

This is where the great kings of Mercia were being buried.

NARRATOR: Anglo-Saxon Chronicles confirmed that this crypt once

contained the remains of three Mercian royals,

making it perhaps the greatest prize for the invading Vikings.

HORTON: Not only would it be dripping with treasures,

but actually, more importantly,

once they've captured this, they've captured

the soul of Saxon England.

That explains why some of their dead

are buried in those mounds.

[men shouting]

NARRATOR: In 874 AD,

the heathen warriors conquer Mercia and descend

on Wessex, the last Saxon kingdom.

There were thousands of Vikings in a coordinated effort,

acting as a unified army coming right at them.

NARRATOR: The two armies meet at the battle of Eddington

where the Wessex king,

Alfred the Great, finally defeats the Norsemen,

ending their campaign of conquest.

Alfred goes on to unite the four kingdoms,

and the bodies of

the vanquished heathens are swallowed by the earth before

being revealed once more from the skies.

HORTON: What I've seen has made me totally certain that

the Vikings came here,

and in so doing, changed the course of

English history.

NARRATOR: Coming up, the Navy's multibillion dollar secret.

This is something being used for very special purposes.

NARRATOR: And Hawaii's mystery cipher.

ALBERTSON: It reminds me sort of like a chess game.

I don't get it.

NARRATOR: September 2020,

a satellite captures this image of

New Jersey's 7,400-acre Lakehurst Naval Base.

HYMEL: We're looking at what looks to be an airstrip.

No surprise there.

But north of it, we see these five lines,

almost like a section of a fan,

and a cutout sort of circular pattern.

MORGAN: These shapes don't seem like they go together,

and I'm not sure what they're for.

♪

NARRATOR: Lakehurst is one of the U.S. military's

most sophisticated testing facilities,

with a history stretching back over 100 years.

Military records reveal that the strange circle in

the image is the legacy of its darkest hour.

Despite the fact that this is a Naval Air Research Center,

what is interesting is that the big circle in

the image is the landing site of the Hindenburg.

NARRATOR: When launched in 1936,

the 800-foot-long German airship,

partly funded by the Nazis,

was seen as the future of luxury air travel.

In a cabin sitting below some seven

million cubic feet of highly flammable hydrogen,

50 passengers enjoy a piano bar,

fine dining, and incredibly, a smoking lounge.

HYMEL: The blimp is ideally suited for this task.

It can stay elevated for long periods of time

without any kind of heavy fuel consumption.

NARRATOR: On May 6th, 1937, the mammoth airship

approaches Lakehurst after completing

a transatlantic flight.

As it attempts to dock at the circle

in the image, it ignites,

and the resulting inferno claims 36 lives.

ALBERTSON: In the middle, they would have had a hook

that the airship would have hooked on to be stable and land.

It also would have discharged any static electricity

into that when it landed,

which eventually led to the crash.

NARRATOR: The strange lines to the south of

the crash site have a different origin.

MORGAN: When you punch in close,

you can see that these fan-shaped lines look like

airstrips maybe, but they converge.

CAVELL: You can actually see tracks in the middle of them.

This is something being used for very special

military purposes.

NARRATOR: Declassified records confirm

the tracks are used to help

the military prepare for the extraordinary challenges

posed by naval aviation.

Naval aviation really means planes flying off

the deck of a carrier or landing.

CAVELL: It's probably one of the most

dangerous occupations to be involved in.

Just about every aspect of it could

be deadly if you slip for one minute.

NARRATOR: The first attempt to launch a plane from a warship

takes place in 1910,

just seven years after the Wright brothers' maiden flight.

Over the following decades,

thousands of Navy pilots die attempting

this perilous maneuver.

ALBERTSON: Think about what it takes to land aircraft, right?

Now go to sea with pitching decks,

rough seas of 50 feet or greater --

one wrong move at the wrong moment

will get you dead, and this happens every year.

NARRATOR: Following World War II,

the advent of supersonic jets forces the Navy

to introduce a new generation of carrier deck technologies.

The systems on an aircraft carrier that launch

and catch aircraft

are incredibly complex, and the catapult is probably

the most important.

NARRATOR: The latest generation of aircraft carriers

uses electromagnetic launch systems.

Before being installed on flight decks,

the systems are tested to the point of destruction

at the site in the image using rocket-propelled sleds.

MORGAN: The jet car track site provides the ability to test

at high speed on the ground

without having to hazard expensive aircraft

or lives in an airborne test.

NARRATOR: On board, these systems propel $100 million

fighter jets 0 to 165 miles per hour in two seconds,

subjecting pilots to a dizzying 4 Gs of force.

MORGAN: You can get a large twin engine jet fighter, like

an F-18, airborne in a span of a couple hundred feet.

NARRATOR: When pilots return from their missions,

Lakehurst-designed cable systems stop

a 150-mile-per-hour jet in less than 300 feet,

transferring four times its takeoff weight

into the fuselage.

CAVELL: They have arrestor cables

that can catch the tail hook on an aircraft,

and the only pieces of equipment

stopping that aircraft from actually plowing

right off the other end of the deck.

ALBERTSON: Room for error does not exist in this business.

It's precision, life or death stuff.

NARRATOR: Eight decades ago, the shapes

and the image were a place of death and terror.

Today, they are vital to protecting

the lives of around 7,000 Navy top guns.

CAVELL: It really is a pretty amazing facility

at the cutting edge of military technology.

NARRATOR: Coming up, China's mystery mega structures.

The spies go there disguised as tourists

to figure out what they actually are.

NARRATOR: And the strange tale of the mule that tried to

save America.

CAVELL: It would be the first line of defense

in any kind of an attack.

NARRATOR: February 23rd, 2020.

A spy bird in orbit over South China's

Fujian province captures these structures

in the landscape below.

MORAN: This is a really perplexing image.

You have this cluster of shapes, but they don't seem

to be arrayed with any kind of rhyme or reason.

MUNOZ: The location is also really strange.

There's nothing around it except for forests.

Someone really had to go to

a lot of effort to build these things.

NARRATOR: What's even weirder is that

declassified files reveal the CIA

took a great interest in these structures during the 1960s.

There are spy satellite images of this exact location,

which means that CIA analysts were actively looking at

this area and wondering themselves

what was going on there.

CAVELL: The regularity of the structures and the clustered

nature of them were red flags to people

at the CIA who were really worried about what kind of

strategic purpose these might have had.

NARRATOR: The CIA knows that China has just become

a nuclear power by

detonating a 22-kiloton nuclear device

code named Project 596.

The intelligence agency fears the mystery structures are

evidence of a dramatic escalation

in their nuclear capabilities.

MORGAN: The government was worried that the Chinese

had not only developed an atomic bomb,

but that maybe these structures were

the launch site for ICB EBs.

NARRATOR: Washington is already engaged

in a silent yet hugely costly

conflict with Russia and is

about to send troops into Vietnam.

Now, it has another

terrifying threat to contend with,

one that it fears could strike at any target within the U.S.

The reason that the government had to be so concerned about

this was that that would represent

a significant challenge to the balance of power,

and the balance of power circa 1965

was already pretty delicate.

NARRATOR: What's more, China's secret development

of its atomic program infuriates Russia,

creating a three-way standoff

between the nuclear superpowers.

MORAN: Here, you have escalating tensions between

the U.S. and the Soviet Union,

and suddenly, there's another country in

that region developing its own nuclear capability.

It's worrisome for everyone.

NARRATOR: The Cold War satellite images reveal thousands

of the silo-like structures scattered across China.

If these are nuclear silos,

the CIA has got to find out more.

MORGAN: Satellite photography ultimately led to spies

having to go there disguised as tourists

to figure out what they actually are.

NARRATOR: The spies confirm that the structures

and the image do serve a military function,

but not the one the intelligence agency expected.

CAVELL: What becomes clear is that these are traditional

Hakka fortifications

and that many of them have actually been around for more

than 600 years.

NARRATOR: The Hakka are an ethnic Chinese

people whose origins are shrouded in mystery.

According to folklore,

they are descended from some of

the most celebrated warriors in the country's history.

The Hakka have traditionally been linked

to one of the greatest and most warlike

of the Chinese dynasties, the Qin dynasty.

NARRATOR: The Qin Dynasty rises to power

during the 3rd century BC.

Its founder, Emperor Qin Shi Huang,

conquers the six warring states of China,

creating a unified country for the first time.

On his death, a city-sized mausoleum is built in

his honor, guarded by the 8,000 soldiers of the Terracotta Army.

HYMEL: Legends had it that the Hakka people

are descendants of warriors from Qin's army.

So there's this strong connection between the Hakka

people and one of the great emperors of China.

NARRATOR: Unlike many Chinese,

the Hakka have no traditional homeland.

As they move from province to province,

they become viewed as outsiders and are

forced to migrate south to escape persecution.

The Hakka people in later times found themselves

under attack.

The dangers of just trying to exist

and raise a family were very great.

NARRATOR: After centuries of oppression,

a group of Hakka arrive in Fujian province,

seeking refuge in its remote mountainous interior.

Yet even here, they find no sanctuary.

Bandits ran wild in this region of China,

which made life pretty miserable for the Hakka.

With everyone against them,

it's only natural to assume that the Hakka would consider

building some serious defenses.

NARRATOR: During the 13th century AD,

the Hakka begin constructing the structures

in the image, known as tulous,

to defend their families from the constant

threat of violence.

MORGAN: What they developed was a perfectly circular structure

with very robust outer walls

that could be used for defensive purposes.

MUNOZ: These structures were built to withstand anything,

fires, attacks,

you name it, they were prepared for it.

NARRATOR: Each of the fortified buildings is designed to

hold up to 800 Hakka warriors and their families,

and enough supplies and weaponry is to repel

anything from a surprise attack to a prolonged siege.

They had a background, a proud background, of a warrior

tradition, and these buildings, they speak to that tradition.

NARRATOR: The strange structures that so terrified the CIA

are, in fact, the legacy of

one of the most extraordinary and resilient groups of people

in all of China.

What we're seeing here is actually a testament to

the tenacity and the sheer will

of a marginalized people just wanting to survive.

♪

NARRATOR: Coming up, the forgotten heroes

of Pearl Harbor.

It is a remarkable end to a really dramatic tale.

NARRATOR: And the mutant lake.

It's almost as if it's a creature

living out its life cycle.

NARRATOR: September 16th, 2020.

As a satellite orbits above Ni'ihau,

the westernmost island in the Hawaiian archipelago,

it captures this pattern far below.

This is really an extraordinary image.

RUBEN: All across are these giant grids,

just crisscrossing lines like graph paper

underneath the land.

NARRATOR: The crisscrossing lines cover

some 370 acres of a dry lake bed.

ALBERTSON: It reminds me sort of like a chess game set out on

the ground -- I don't get it.

NARRATOR: The lake is called Halulu,

named after a mythical man-eating bird by the first

Polynesian settlers who arrived here some 1,500 years ago.

And they came to places like Hawaii

to try to set up agricultural settlements.

Squares like this are common for dividing up farmland.

Could it be agricultural plots?

NARRATOR: Yet when Adam Ruben reviews local land records,

he discovers the strange lines don't appear until the 1930s.

This was a time when Hawaii was particularly concerned

about the build-up to a second World War.

So this coincidence of timing indicates that maybe

the lines have something to do with the war.

NARRATOR: The records confirm that the satellite has captured

a bizarre relic of

one man's attempt to repel the might of the Japanese

Imperial Navy.

A local ranch owner decided that instead of waiting for

a Japanese invasion,

he would take matters into his own hands.

CAVELL: It's kind of amazing.

I mean, he was protecting an entire island,

and maybe even an island chain, from a potential attack.

NARRATOR: The story of the strange ruts

begins in the aftermath of World War I, when the League

of Nations grants Japan territories in the Pacific.

That puts the empire of Japan sort of on a collision course

with the United States,

because the United States is also occupying parts of

the Pacific, and the two countries are beginning to

rival one another.

NARRATOR: In 1930s, Japan begins a period of rapid military

expansion, which will see it

take over parts of China and the Soviet Union.

With more than 40 percent of its population of Japanese descent,

Hawaii is directly in

the firing line of these Imperialist ambitions.

The Japanese looked toward the Hawaiian islands as being

a place where they could potentially establish

an overseas empire.

People on the islands are certainly feeling the impact

of this increased tension.

NARRATOR: Yet few in the U.S.,

including President Roosevelt, believe the Japanese

possess the military strength needed to threaten U.S. soil.

There is a lot of thinking among,

especially naval planners, that there

is no way that Hawaii would be directly vulnerable

to an attack.

MORGAN: Most people were sort of content to ignore the Pacific.

It didn't show up in the headlines.

It was a third page matter.

NARRATOR: Despite Washington's apparent

rejection of the Japanese, threat among the Hawaiians,

fear continues to grow.

HYMEL: Everyone in the Hawaiian islands is concerned,

but it's the island of Ni'ihau,

the most northern western island, where the fear is

the most intense.

It would be the first line of defense

in any kind of an attack.

NARRATOR: In 1933, a local landowner identifies

the lake bed in the image as

a potential natural runway for a Japanese invasion

and decides to act.

What he decided to do was dig up

acres and acres and create

this grid system of trenches

that would prevent the dry lake beds from becoming

the perfect landing strip for Japanese aircraft.

HYMEL: If a Japanese plane tries to land,

it's gonna hit these furrows and either crack up on

landing or maybe even flip over and pancake,

as the pilots call it.

NARRATOR: A small team of Islanders uses shovels

and a plow to carve out

half a square mile of 2-foot-deep deep ruts

across the lake bed, revealed from space.

Rutting up these lake beds is no small undertaking.

It's going to take some back-breaking manual labor.

Some people might have looked at him as crazy,

but there really is a pretty impressive foresight that he

sees the coming war

and creates this defense that will deny

the Japanese any idea of using this as a forward base.

NARRATOR: On December 7, 1941, the maverick rancher's fears

are realized when 360 Japanese aircraft rain down

terror on Pearl Harbor.

[explosion blasts]

[gunfire]

NARRATOR: In the aftermath, a damaged Mitsubishi Zero

heads for Ni'ihau,

how hoping to land in the lake bed in the image.

His plan is to put his aircraft down and then rejoin

the fleet -- well, his plans are gonna be foiled

by the trenches.

NARRATOR: The rutted lake bed forces the pilot to crash land,

and he is detained by the islanders,

one of the only Japanese prisoners captured

during the infamous assault on Pearl Harbor.

It really is kind of a remarkable end

to a really dramatic tale.

MORGAN: And that's why the ruts are in the lake.

And those ruts can still be seen

to this day, almost 80 years later.

NARRATOR: Coming up, America's toxic time bomb.

This is a very dangerous situation here.

NARRATOR: More than 150 Earth observation satellites

orbit our planet,

mapping its ever-changing surface in

extraordinary detail.

KOUROUNIS: One great thing about satellite imagery is that

we can look at pictures

from different periods of time and see how

the Earth's surface has changed.

NARRATOR: A series of these images taken

over Green Township, Pennsylvania, uncover a mystery.

There's something really unusual about this lake.

RUBEN: Looking across time, this body of water,

it's growing and shrinking.

It's changing shape, it's changing color.

It's almost as if it's a creature

living out its life cycle.

NARRATOR: What's more, analysis reveals the lake's

morphing waters are forcing those living nearby to flee

their homes.

If we look around this lagoon,

we don't really see signs of life.

The buildings look abandoned.

PATEL: It's a bit eerie.

It kind of makes you wonder if there's something unsafe here.

NARRATOR: Samples taken from the mutating lake

confirm that its waters are highly toxic.

It's a cocktail of arsenic and mercury

and lead, things that can really harm human health.

This water is basically a poison stew.

NARRATOR: The roll call of deadly metals offers a clue

to the lake's origin.

We can trace the toxic minerals that are coming from

this particular pond to

the waste products from a power plant,

something called coal ash.

NARRATOR: Coal ash is a highly noxious waste, created when

power plants incinerate vast amounts of the fossil fuel.

And the two states bordering the lake produce

over 20 million tons of the stuff each year.

Whenever you burn coal to generate power,

that coal combusts, and what's left behind is a mixture of

various impurities and chemicals that basically

have to be stored somewhere.

LESTER: Typically, it is dissolved or mixed with water

and disposed of in holding ponds or lakes.

NARRATOR: Back in 1974,

authorities tell locals they are creating

a boating lake at the site in the image.

Over the next 40 years,

they fill it with 20 billion gallons of noxious

coal ash slurry.

Chemicals in the effluent generate colors

so vivid, they are visible from space.

It completely makes sense,

now, understanding what's in this lagoon,

that these buildings are abandoned.

The substances in coal ash can cause all kinds

of problems, and it has absolutely

devastated the community.

NARRATOR: Over the years, the lake in the image grows

to become the biggest waste dump in the U.S.,

and it's just one part of

an unfolding disaster that could threaten

millions of lives.

These coal ash ponds are a big problem across the U.S.

RUBEN: There are more than a thousand of these sites

around the country, many of them built

without the necessary safety standards.

♪

NARRATOR: The coal ash catastrophe engulfing America

is a legacy of the country's extraordinary

industrial growth over the past two centuries.

Between 1840 and 2010, the U.S. population increases

from some 17 million to over 300 million.

During the same period, coal production surges from

2.5 million tons per year to over one billion.

RUBEN: In many ways, coal is a double-edged sword.

It has enabled the Industrial Revolution.

Coal fueled America for a long time.

But coal has consequences.

NARRATOR: Today, energy companies dispose of 140 million

tons of coal ash each year,

enough to fill a line of train cars stretching

halfway around the world.

More than 95 percent of dump sites are unlined,

and over 200 ash lakes have

contaminated local water supplies with

deadly pollutants.

Cancer, your lungs, kidneys, heart --

all of those things can be damaged

by exposure to these kind of toxic minerals.

This is a very dangerous situation here.

KOUROUNIS: These disposal sites are a real problem,

and the thing that bothers me is

there's almost no federal regulation of them.

NARRATOR: Aerial images reveal how this lack

of regulation can have catastrophic consequences.

In 2008, an ash pond levy

in Kingston, Tennessee, collapses,

flooding a nearby town with over a billion gallons of

contaminated sludge.

It's the largest industrial disaster in U.S. history,

releasing five times as much toxic

material as the Deepwater Horizon oil spill.

It is just an awful tragedy

that has befallen the community here.

Unless we start to take into account

that these things are dangerous,

we're gonna continue to see lots of deaths,

lots of health problems in general,

by the people living next to these coal ash ponds.

NARRATOR: In 2016, authorities begin to

clean up the site in the image,

but elsewhere, around six million American lives

live within the deadly shadow of ash ponds,

and for many, time is running out.

RUBEN: We need power to run this country,

and we need reservoirs to create that power,

and that's all well and good until it's your town

that ends up at the bottom of a lake.