Narrator: PARIS -- A CITY OF ARCHITECTURAL WONDERS...
...AND ICONIC ART.
BUT PARIS IS UNDER THREAT.
THIS CRACK IS ENORMOUS.
WHOA.
THIS CITY IS COLLAPSING.
THERE ARE DEADLY CAVERNS OPENING UP UNDER THE STREETS.
THIS DOESN'T LOOK VERY SAFE.
QUITE THE SHOCK THAT THEY BUILT A CITY
ON TOP OF ALL THESE HOLES.
Narrator: HOW CAN PARIS SURVIVE?
TO FIND OUT, WE WILL STRIP THE CITY
TO REVEAL ITS SECRET, INNER WORKINGS
AND EXPOSE THE INGENIOUS TECHNOLOGY
THAT ALLOWED ENGINEERS
TO BUILD THIS CITY ON THE BRINK OF DISASTER.
-- Captions by VITAC -- www.vitac.com
CAPTIONS PAID FOR BY DISCOVERY COMMUNICATIONS
PARIS, THE CITY OF LIGHT.
FULL OF STUNNING LANDMARKS, ANCIENT AND MODERN.
EVERY YEAR, 30 MILLION VISITORS ARRIVE
TO MARVEL AT ITS WONDERS.
[ CAMERA SHUTTERS CLICKING ]
BUT PARIS' ICONIC STRUCTURES ARE UNDER THREAT.
THE CITY'S STREETS ARE AT RISK OF COLLAPSING
INTO GIANT UNDERGROUND HOLES.
CLAMART, 1961, A SUBURB SIX MILES FROM THE CITY'S CENTER.
A VAST CAVITY SWALLOWED SIX STREETS.
21 PEOPLE DIED.
[ DOG BARKING ]
MARCH 1991, CHAMPS DE LUNE LE VIE, NORTHWEST OF PARIS.
ENTIRE HOMES FELL INTO A 100-FOOT-WIDE VOID.
PARIS' STREETS HAVE BEEN COLLAPSING FOR 200 YEARS.
THE PROBLEM -- ALMOST 200 MILES OF ABANDONED,
CRUMBLING QUARRIES THAT SNAKE BENEATH THE CITY.
GEOPHYSICISTS LIKE JOHN ARMITAGE
KNOW THAT PARIS SITS ON A TIME BOMB.
Armitage: THESE UNDERGROUND CHAMBERS
ARE THE HIDDEN DANGER BENEATH PARIS.
THIS USED TO BE A PILLAR THAT SUPPORTED UP HERE,
AND IT HAS VANISHED.
AND EVERYTHING HAS COLLAPSED AT MY FEET.
IF I KNEW THAT I LIVED ABOVE SOMETHING LIKE THIS,
I WOULD SELL MY HOUSE.
Narrator: BEHIND PARIS' DOWNFALL
IS THE VERY ROCK THAT BUILT THE CITY -- LIMESTONE.
THREE QUARTERS OF THE BUILDINGS IN PARIS
ARE CONSTRUCTED FROM IT.
FROM PONT NEUF BRIDGE TO THE LOUVRE GALLERY,
NOTHING BETTER ILLUSTRATES PARIS' ADDICTION TO LIMESTONE
THAN NOTRE-DAME CATHEDRAL.
THE 12th-CENTURY CHURCH TOWERS 314 FEET ABOVE PARIS.
28 SUPPORTS, CALLED FLYING BUTTRESSES,
PROP UP THE WALLS OF THIS 850-YEAR-OLD GOTHIC MASTERPIECE.
THEY SPAN THE LENGTH OF THE 420-FEET LONG LIMESTONE CHURCH.
AND IN THE CRYPT, MORE LIMESTONE --
THE RUINS OF THE 2,000-YEAR-OLD ROMAN CITY OF LUTETIA.
LIMESTONE IS THE IDEAL BUILDING MATERIAL...
...DURABLE, YET EASY TO CUT AND CARVE.
AND IT'S MORE THAN FOUR TIMES STRONGER THAN MARBLE.
A SLICE OF GEOLOGICAL LUCK ENSURES THAT PARIS SITS
ON VAST RESERVES OF THIS PRECIOUS STONE.
45 MILLION YEARS AGO,
PARIS WAS SUBMERGED UNDER A WARM, SHALLOW SEA.
OVER MILLIONS OF YEARS, LAYERS OF SEDIMENT
AND MICROORGANISMS BUILT UP ON THE SEABED.
AS THE DEPOSITS GREW THICKER,
THEY COMPRESSED TO FORM A SOLID LAYER OF ROCK -- LIMESTONE.
[ CREAKING ]
THE SEA DRAINED AWAY, BUT PARIS' FAMOUS ROCK REMAINS.
AND NOW THIS THICK LAYER OF LIMESTONE
SITS JUST 60 FEET BENEATH THE SURFACE OF THE CITY.
INCREDIBLY, THE LIMESTONE QUARRIES THAT BUILT PARIS
AREN'T ALL OUT IN THE SUBURBS.
THEY'RE DIRECTLY UNDER THE CITY STREETS...
...AS QUARRY EXPERT GILLES THOMAS EXPLAINS.
A HIDDEN PARALLEL WORLD OF ALMOST 200 MILES OF TUNNELS
AND CAVERNS SNAKE RIGHT BENEATH THE HEART OF PARIS.
THE VOIDS CUT BENEATH 10% OF THE CITY.
THEY ARE THE REMNANTS OF THE CENTURIES-OLD QUARRIES.
THE CITY'S PROBLEMS BEGAN WHEN IT EXPANDED
ON TOP OF THESE ABANDONED QUARRIES.
NOW THEY'RE COLLAPSING UNDER THE WEIGHT OF THE WORLD ABOVE.
AROUND 12 STREETS A YEAR HERE SHOW SERIOUS SIGNS OF COLLAPSE.
ENTIRE BUILDINGS AND SUBURBS ARE AT RISK.
NOW PARIS IS FIGHTING BACK.
[ SPEAKING FRENCH ]
A WHOLE TEAM OF ENGINEERS RACE TO REPAIR
THE CRUMBLING CAVERNS BENEATH THE CITY --
THE INSPECTION GéNéRAL DES CARRIèRES.
GEOLOGICAL ENGINEER ANNE-MARIE LEPARMENTIER LEADS THE WORK.
[ SPEAKING FRENCH ]
Narrator: TODAY, DR. JOHN ARMITAGE
JOINS THE REPAIR CREW AS THEY EXPLORE A QUARRY
THAT'S CLOSE TO COLLAPSE IN THE EAST OF THE CITY.
OKAY.
ANNE-MARIE SHOWS JOHN JUST HOW FRAGILE THE MINE IS.
[ ROCKS CLATTERING ]
[ SPEAKING FRENCH ]
Interpreter: HERE, WE HAVE A STONE PILLAR
UNDER HUGE VERTICAL STRAIN.
IT HAS BROKEN ALL THE WAY TO THE BASE, MUCH MORE THAN EXPECTED.
Narrator: IT'S NOT JUST THE PILLARS.
THE ROOF OF THE QUARRY IS CRUMBLING
UNDER THE WEIGHT OF THE CITY ABOVE.
THIS IS PRETTY DANGEROUS.
YES, IT'S VERY DANGEROUS.
Armitage: IN FRONT OF ME, THERE ARE TWO LARGE AREAS
THAT HAVE FRACTURES DOWN THE BACK OF THEM,
FRACTURES ON THE SIDE OF THEM.
IN FACT, THEY'RE PRIMED TO COLLAPSE.
IN FACT, I'M NOT HANGING OUT HERE ANY LONGER.
I'M OFF.
Narrator: THE ANCIENT PILLARS PROPPING UP THESE MINES
WERE BUILT BY MANY GENERATIONS OF MINERS,
FROM ANCIENT ROMANS TO MEDIEVAL QUARRYMEN.
THE SUPPORTS IN THIS MINE
ARE SHOWING DANGEROUS SIGNS OF DISINTEGRATION.
TO BRACE THEM, ANNE-MARIE'S TEAM
ENCASES THEM WITH MORE LIMESTONE.
AND THEY BUILD STURDY,
NEW PILLARS ALONGSIDE TO SPREAD THE LOAD.
IT'S A HUGE TASK
BUT THE ONLY WAY TO STOP PARIS FROM CAVING IN.
BUILDING THE SUPPORTS IS BACKBREAKING WORK.
IT'S IMPOSSIBLE TO SQUEEZE HEAVY MACHINERY
INTO THIS RESTRICTIVE, ANCIENT QUARRY.
SO THE TEAM MUST DO ALL THE WORK BY HAND.
Interpreter: IT'S VERY PHYSICAL, HARD WORK.
HUMIDITY'S AT OVER 90%.
Narrator: FOR OVER 230 YEARS,
ENGINEERS HAVE BEEN KEEPING PARIS STANDING
BY BUILDING PILLARS AND FILLING CAVERNS WITH CONCRETE.
IT'S AN ONGOING BATTLE
BUT CRUCIAL FOR THE SURVIVAL OF THE CITY.
ONE PROBLEM SOLVED.
AS THE CITY GROWS, ARCHITECTS NEED TO BUILD UP.
CONSTRUCTING TOWERS AND SKYSCRAPERS
ON THIS UNSTABLE GROUND IS A RECIPE FOR DISASTER.
Narrator: THE EIFFEL TOWER -- "THE OLD LADY OF PARIS."
DESIGNED AND BUILT
FOR THE INTERNATIONAL EXHIBITION OF 1889,
ORIGINALLY, IT WAS TO STAND FOR JUST 20 YEARS.
BUT IT REMAINS THE MOST ICONIC STRUCTURE IN THE CITY
125 YEARS AFTER ITS CONSTRUCTION.
SOARING MORE THAN 1,000 FEET...
...IT WAS THE TALLEST STRUCTURE IN THE WORLD FOR OVER 40 YEARS.
[ METAL CREAKING ]
2 1/2 MILLION RIVETS HOLD TOGETHER
18,000 PIECES OF WROUGHT IRON.
AT ITS CORE, THREE PLATFORMS,
HOSTING UP TO SEVEN MILLION VISITORS A YEAR.
ANCHORING THE TOWER INTO THE GROUND
WAS A BIG CHALLENGE FOR ITS DESIGNER, GUSTAVE EIFFEL.
THE EARTH DIRECTLY UNDERNEATH THE TOWER
IS PARTICULARLY UNSTABLE.
IT'S MADE UP OF LAYERS OF LOOSE EARTH, CALLED "MARL."
Armitage: THIS IS HERE IS MARL.
IT IS A SOFT CALCIUM-RICH CLAY THAT LIES ABOVE THE LIMESTONE.
IT POSES A PROBLEM FOR CONSTRUCTION IN PARIS
BECAUSE IT'S SO SOFT.
AND SO, WHEN YOU BUILD FOUNDATIONS,
YOU MIGHT FIND THAT THE GROUND IS UNSTABLE,
AND SO YOU CANNOT BUILD VERY TALL, HIGH STRUCTURES.
Narrator: TO SECURE THE TOWER INTO THE SOFT MARL...
[ METAL CREAKING ]
...EIFFEL'S WORKERS FIRST DUG A SERIES OF SHALLOW PITS.
INSIDE, THEY ENCASED TWO STEEL ANCHOR BOLTS
IN BLOCKS OF STONE AND CEMENT.
THEY ANGLED THE BLOCKS TOWARDS THE TOWER'S LEGS.
THESE BLOCKS SPREAD THE 7,500-TON WEIGHT OF THE TOWER
EVENLY ACROSS THE UNSTABLE GROUND,
PREVENTING IT FROM SINKING.
INCREDIBLY, EACH BLOCK EXERTS LESS PRESSURE
ON THE EARTH BELOW IT THAN A HIGH HEEL.
IT TOOK EIFFEL JUST TWO YEARS TO CONSTRUCT HIS TOWER,
USING PRE-FABRICATED IRON GIRDERS.
THIS METAL LATTICE DESIGN
MAKES THE STRUCTURE STRONG AND LIGHTWEIGHT.
TODAY, ENGINEERS STILL USE A LIGHT TOUCH
TO BUILD TALL IN PARIS.
IN LA DéFENSE, THE CITY'S FINANCIAL DISTRICT...
...CONSTRUCTION CREWS ARE HARD AT WORK.
THEY'RE BUILDING 12 NEW SKYSCRAPERS
OVER THE NEXT SIX YEARS
THAT WILL TRANSFORM THE CITY'S SKYLINE.
THE D2 TOWER IS ONE OF THE MOST STRIKING.
JUST 21 FLOORS TO GO.
Narrator: ANTHONY BECHU AND TOM SHEEHAN ARE D2's ARCHITECTS.
WE'RE PRACTICALLY AT THE SUMMIT AT THE TOWER.
WE'RE JUST ABOUT A YEAR AWAY FROM BEING FINISHED.
IT'S DIFFICULT TO IMAGINE THAT
WHEN YOU CAN SEE THE CONSTRUCTION
IN THE STATE THAT IT'S IN.
Narrator: BUILDING THE D2 TOWER IS NO SIMPLE TASK.
THE CONSTRUCTION SITE IS HEMMED IN.
Sheehan: A TOWER IS LIKE SENDING A ROCKET TO THE MOON.
IT'S EXTREMELY COMPLICATED.
IT NEEDS AN ENORMOUS AMOUNT OF PLANNING PRIOR TO DOING IT.
IF YOU COULD CHOSE ANYWHERE TO BUILD,
YOU WOULDN'T BUILD IN LA DéFENSE.
YOU'D BUILD SOMEWHERE OUT IN THIS FIELD
WHERE YOU HAD NOTHING AROUND IT.
IT'S MUCH EASIER TO DO.
Narrator: DIGGING DEEP FOUNDATIONS
INTO THE UNSTABLE GROUND HERE IS EXTREMELY RISKY.
THE FOOTINGS COULD CAVE IN
AND CAUSE NEARBY TOWERS TO LEAN OR EVEN FALL.
SO THE TEAM SINKS 90 CONCRETE PILES
INTO A LAYER OF LIMESTONE 65 FEET DOWN.
A THIN CONCRETE SLAB SUPPORTS THE BUILDING'S CONCRETE CORE.
FLOORS MADE FROM SOLID METAL PLATES
AND A STEEL LATTICE FRAME
COMPLETE ITS LIGHTWEIGHT STRUCTURE.
4,000 GLASS PANELS FORM THE SKIN
OF THIS STUNNING, 561-FEET-TALL SKYSCRAPER.
ERECTING THE TOWER'S STEELWORK IN THIS CRAMMED SPOT
IS A DAUNTING JOB FOR THE CRANE CREW.
Sheehan: THE FOOTPRINT OF THE TOWER
IS LESS THAN 3,000 SQUARE METERS.
SO IT'S EXTREMELY COMPLICATED.
Narrator: STRONG GUSTS MAKE THE MISSION EVEN TOUGHER.
Mertens: THE "V" IS SIX TONS.
WHEN IT'S COMING UP AND THERE'S A LOT OF WIND,
IT CAN TURN WITH ONE OF ITS LEGS.
WE MUST DO IT VERY SLOWLY, YEAH.
Narrator: THE TOWER CURVES AT THE TOP.
THIS RESTRICTS THE WORKSPACE FOR THE CREW EVEN FURTHER
AND MAKES ATTACHING EACH BESPOKE PIECE OF STEEL MUCH TOUGHER.
Sheehan: WE'RE AT A CRITICAL STAGE
IN THE LIFTING UP OF THE STRUCTURE.
AT THE PART WHERE IT'S PRACTICALLY THE MOST TAPERED,
EACH PIECE IS SPECIALLY DESIGNED.
THERE'S VERY LITTLE REPETITION,
AND SO IT'S A BIT MORE COMPLICATED.
[ SPEAKS FRENCH ]
IT'S GOING TO BE A REALLY SPECTACULAR BUILDING.
IT'S NOT THE HIGHEST TOWER IN PARIS.
IT'S NOT THE MOST VISIBLE TOWER IN PARIS.
BUT I THINK IT'S PROBABLY GONNA BE
ONE OF THE MOST BEAUTIFUL TOWERS IN PARIS.
[ SPEAKS FRENCH ]
Narrator: ONCE COMPLETE, THIS GLASS GOLIATH
WILL SOAR ABOVE THE CITY...
...ITS STEEL FRAMEWORK ECHOING THE WORK OF GUSTAVE EIFFEL
OVER A CENTURY AGO.
IT WILL JOIN THE 11 OTHER SKYSCRAPERS
TO FORM A TRIUMPHANT, NEW HORIZON FOR PARIS.
THE FINANCIAL DISTRICT OF TOMORROW
WILL ACCOMMODATE MORE PEOPLE THAN EVER BEFORE.
BUT AS THE CITY EXPANDS,
IT NEEDS TO IMPROVE ITS TRANSPORTATION SYSTEM, AS WELL.
AND THIS MEANS DIGGING FURTHER INTO PARIS' UNSTABLE EARTH
TO EXTEND A METRO NETWORK THAT'S ALREADY ON SHAKY GROUND.
Narrator: PARIS...
[ CAR HORNS HONKING ]
...EARLY-MORNING RUSH HOUR.
10 MILLION COMMUTERS FROM THE CITY AND THE SUBURBS
BEGIN THEIR DAY.
ALMOST HALF OF THEM WILL USE THE CITY'S CROWDED METRO.
BOASTING 300 STATIONS AND OVER 130 MILES OF TRACK,
IT'S THE SECOND-BUSIEST METRO NETWORK IN EUROPE.
THIS IS ONE OF ITS MAJOR HUBS, GARE DU NORD.
MORE THAN 282 MILLION COMMUTERS TRAVEL THROUGH IT EVERY YEAR.
OPENED IN 1846,
IT HAS GROWN TO BECOME THE BUSIEST TRAIN STATION IN EUROPE.
28 MAIN-LINE PLATFORMS SIT ABOVE GROUND.
FOUR METRO LINES RUN UNDERNEATH.
BELOW THEM, THE CITY'S NETWORK OF ANCIENT QUARRIES.
SOME ARE NOW FILLED IN FOR THE SAFETY
OF THE 770,000 PEOPLE THAT USE THE GARE DU NORD EVERY DAY.
[ BRAKES SCREECH ]
BUT IN PARIS' 13th DISTRICT, THE CRUMBLING QUARRIES
PUT THE METRO LINES IN IMMINENT DANGER.
TODAY, GEOPHYSICIST JOHN ARMITAGE JOINS ENGINEERS
FROM THE INSPECTION GéNéRAL DES CARRIèRES...
[ SHOUTS ]
Narrator: ...TO EXAMINE THIS ABANDONED QUARRY TUNNEL.
[ CONVERSING IN FRENCH ]
IT SITS DIRECTLY UNDER METRO LINE SEVEN.
Armitage: THIS DOESN'T LOOK VERY SAFE.
Narrator: THEY'RE LOOKING OUT FOR CRACKS.
Armitage: [ SPEAKS FRENCH ]
WE'RE ROUGHLY HERE, AND WE'RE GOING TO TAKE A TOUR
THROUGH THESE GALLERIES DOWN TO HERE.
[ SHOUTS ]
Narrator: SPACE IS TIGHT UNDERNEATH PARIS.
THE METRO TUNNELS RUN AS CLOSE AS 3 FEET BELOW THE PAVEMENT
AND 14 FEET ABOVE THE QUARRIES.
[ RUMBLING ]
CRACKS COULD BE A SIGN THAT THE TUNNEL IS GIVING WAY.
THIS CRACK IS ENORMOUS.
THIS CRACK IS ABOUT TWO METERS LONG.
SO, THESE WALLS SAFEGUARD THE ROCK ABOVE
AND MAKE SURE CRACKS LIKE THIS ONE ARE NOT AN ISSUE
AND THAT THE ROCK ABOVE WILL NOT COLLAPSE DOWN.
Narrator: PARIS DEPENDS ON THE STABILITY
OF ITS UNDERGROUND WORLD.
THE CITY'S ICONIC BUILDINGS ABOVE GROUND
AND THE LABYRINTH OF METRO LINES BELOW
ARE AT RISK OF COLLAPSING INTO THE QUARRIES.
THE SMALLEST HAIRLINE CRACK IN THE QUARRY ROOF
COULD TRIGGER AN AVALANCHE OF ROCK,
DESTROYING EVERYTHING IN ITS PATH...
AND BRINGING PARIS TO A STANDSTILL.
[ GLASS SHATTERING ]
CRAMMED COMMUTER TRAINS PUT THE MAZE OF UNSTABLE CAVERNS
UNDER RELENTLESS PRESSURE.
[ BRAKES SCREECHING ]
SO FOR CENTURIES,
ENGINEERS HAVE BEEN PATCHING UP CRACKS WITH MORTAR
AND BOLSTERING WEAK SPOTS WITH ARCHES.
Armitage: SO, IT'S A CAVITY THAT HAS BEEN REINFORCED,
OR THIS WOULD HAVE BROUGHT DOWN THE METRO LINE,
AND PERHAPS ALSO THE BUILDINGS ABOVE
WOULD HAVE COLLAPSED INTO THE STREETS.
SO THIS LITTLE CONCRETE ARCH
IS A CRUCIAL PIECE OF THE FABRIC OF PARIS.
Narrator: TODAY, FIVE STORIES BELOW THE FINANCIAL DISTRICT,
A MASSIVE $4.5 BILLION PROJECT IS UNDERWAY
TO EXPAND THE CITY'S BUSY METRO.
[ CLACKING ]
A NEW FIVE-MILE TUNNEL WILL LINK CENTRAL PARIS
WITH THE SUBURBAN RAIL NETWORK.
ENGINEERS ARE BUILDING ONE OF THE LINE'S NEW STATIONS
AT THIS SITE.
SQUEEZING IT BETWEEN THE BASEMENT
OF A BUSY SHOPPING MALL ABOVE AND THE UNSTABLE CAVERNS BELOW
IS NO SIMPLE TASK.
DIGGING IN PARIS IS MORE AND MORE DIFFICULT
BECAUSE THERE ARE MORE AND MORE STUFF IN THE GROUND.
THE UNUSUAL PART OF THE PROJECT HERE
IS THAT WE HAVE TO BUILD JUST BENEATH THE BUILDINGS ABOVE,
AND THAT'S THE CHALLENGING PART OF THE PROJECT.
Narrator: CONSTRUCTING THE METRO BENEATH A BUSY SHOPPING MALL
IS TOUGH ENOUGH.
THE MALL'S UNDERGROUND CAR PARK RESTRICTS THE TEAM EVEN FURTHER,
LEAVING THEM WITH JUST A THIN LAYER OF LIMESTONE
TO TUNNEL THROUGH.
DIG TOO SHALLOW AND THE TRAINS WILL ROCK THE MALL.
TUNNEL TOO DEEP AND THE LINE WILL SINK INTO SOFT SAND.
[ CRASHES ]
SO THE TEAM MUST SUSPEND THE NEW STATION
FROM THE BASE OF THE BUILDING'S CAR PARK.
45 CONCRETE COLUMNS WILL SUPPORT THE WEIGHT OF THE MALL ABOVE
AND LOCK THE STATION INTO THE NARROW BED OF LIMESTONE.
THIS CLEVER SOLUTION WILL KEEP BOTH THE MALL AND METRO SAFE.
BEFORE THE TEAM BURROW BENEATH THE MALL,
THEY DIG AN 82-FOOT-DEEP EXPLORATORY WELL.
[ HAMMERING ]
THIS TEST WILL HELP THEM DETERMINE
EXACTLY WHERE THE SOLID LIMESTONE ENDS
AND SOFT SAND BEGINS.
THE LAYER IS VERY IMPORTANT FOR THE DESIGN OF THE STATION
AND THE PROJECT.
WE ARE NOW FACING THE LIMESTONE LAYER.
THAT IS QUITE A GOOD LAYER THAT IS HARD AND VERY DURABLE.
AND THREE METERS FURTHER, WE WILL BE FACING THE SAND LAYER.
THAT IS NOT THAT GOOD.
Narrator: FOR LOUIS' ENGINEERING TEAM,
DIGGING THROUGH THE SLENDER LIMESTONE LAYER
IS LIKE THREADING A NEEDLE.
[ SHOUTS ]
Narrator: WHEN IT OPENS IN 2020,
THE NEW LINE UNDER LA DéFENSE
WILL CARRY 600,000 COMMUTERS A DAY...
...BOOSTING CAPACITY ON ONE OF THE BUSIEST TRANSPORT NETWORKS
IN THE WORLD.
ENGINEERS IN PARIS ARE DEVELOPING INGENIOUS WAYS
TO EXPAND THE CITY UNDERGROUND.
BUT IN THE NORTH OF PARIS,
A MUCH OLDER PART OF THE CITY RISKS TOTAL COLLAPSE.
Narrator: PARIS IS A CITY BATTLING AGAINST COLLAPSE.
SOFT, UNSTABLE ROCK
AND A NETWORK OF ANCIENT UNDERGROUND QUARRIES
THREATEN TO UNDERMINE ITS STREETS AND FAMOUS BUILDINGS.
THE MOST AT-RISK AREA
IS A DISTRICT IN THE NORTH OF THE CITY...
...MONTMARTRE, PARIS' ICONIC HILLTOP NEIGHBORHOOD,
AN ENCLAVE FOR THE CITY'S ARTISTS.
AT ITS SUMMIT, SACRé COEUR.
THIS 280-FOOT-LONG BASILICA WAS CONSECRATED IN 1919
AFTER NEARLY 40 YEARS OF CONSTRUCTION.
THE LANDMARK ATTRACTS MORE THAN 10 MILLION VISITORS EVERY YEAR.
BEHIND THE BASILICA'S WHITE, STONE WALLS
LIES AN ORNATE INTERIOR...
INCLUDING ONE OF THE WORLD'S LARGEST MOSAICS.
AND BELOW GROUND, THE DESIGN IS JUST AS AWE-INSPIRING.
83 STONE PILES ANCHOR THE BUILDING
BEHIND ANCIENT MINES THAT THREATEN THE WHOLE AREA.
THE STONE THAT WAS MINED FROM UNDERNEATH MONTMARTRE
IS NOT LIMESTONE.
IT'S GYPSUM.
Armitage: THIS IS WHAT THE QUARRYMEN WERE AFTER --
GYPSUM UNDER MONTMARTRE.
Narrator: GYPSUM IS ONE OF THE MOST WIDELY USED MINERALS
IN THE WORLD.
LIGHTWEIGHT AND FIRE-PROOF, IT'S USED IN CEMENT,
TO MAKE STATUES, AND IS ALSO THE MAIN INGREDIENT OF DRYWALL.
MINING WAS ONE OF MONTMARTRE'S MAIN SOURCES OF WEALTH
DURING THE 18th- AND 19th-CENTURIES.
BACK THEN, MINES IN NORTHERN PARIS
PRODUCED 2/3 OF THE COUNTRY'S GYPSUM.
THEY EXPORTED IT ACROSS EUROPE AND THE U.S.
TODAY, THE AVERAGE HOME CONTAINS SEVEN TONS OF IT.
Armitage: WHEN THE MINERS WERE GOING FOR THIS GYPSUM,
THEY WANTED TO MAXIMIZE THE MONEY THEY WOULD GET FROM IT
BECAUSE IT'S A CHEAP COMMODITY.
SO THEY WOULD COME IN, STARTING AT THE TOP,
AND TAKE AS MUCH AS THEY COULD ALL THE WAY DOWN TO THE BASE,
LEAVING LARGE CAVERNS BEHIND THEM.
Narrator: BUT ITS POPULARITY COMES AT A PRICE.
OVER-MINING LEFT BEHIND THESE 20-FOOT-TALL UNDERGROUND CHASMS
THAT ARE EXCEPTIONALLY UNSTABLE.
GYPSUM HAS A CATASTROPHIC WEAKNESS.
[ WATER DRIPS ]
IT IS SOLUBLE IN WATER.
I AM GOING TO POUR WATER OVER THIS GYPSUM.
AND IT'S GONNA WORK ITS WAY INTO THE STRUCTURE,
CAUSING IT TO WEAKEN, LOOSEN,
SO THAT YOU CAN PULL OUT PIECES OF THE GYPSUM.
Narrator: GYPSUM QUARRIES BURROW A QUARTER OF A SQUARE MILE
BENEATH NORTHERN PARIS.
TALL GYPSUM PILLARS,
SOME AS HIGH AS FIVE-STORY OFFICE BUILDINGS,
SUPPORT MONTMARTRE.
BUT WATER SEEPS DOWN INTO NATURAL FRACTURES
WITHIN THE ROCK.
IT SLOWLY DISSOLVES THE GYPSUM AWAY,
CAUSING THE QUARRIES TO CAVE IN.
GYPSUM COLLAPSES CAN BE SUDDEN AND DEADLY.
[ DOG BARKING ]
THIS ONE IN 1991 SWALLOWS CARAVANS AND KILLS ONE MAN.
BUILDINGS ALL ACROSS MONTMARTRE SHOW SIGNS OF SUBSIDENCE.
BUT ENGINEERS MUST STILL FIND WAYS
TO EXPAND THE CITY ON TOP OF THIS UNSTABLE EARTH.
THREE MILES EAST OF MONTMARTRE,
A BOLD, NEW BUILDING IS RISING...
...THE PHILHARMONIE DE PARIS,
A COLOSSAL, NEW $520 MILLION CONCERT HALL,
BOASTING A 2,400-SEAT AUDITORIUM.
SUPPORTING THIS BUILDING'S 20,000-TON BULK
ON THE UNSTABLE GROUND TAKES INVENTIVE ENGINEERING.
GEOFFROY VAUTHIER HAS BEEN WORKING ON THE PROJECT
SINCE ITS INCEPTION SIX YEARS AGO.
Vauthier: IT'S VERY EXCITING TO SEE NOW THE REAL CONCERT HALL --
THE BIGGEST CULTURAL PROJECT IN PARIS.
IT NEEDS LIKE 50, 60 ENGINEERS AND 400 WORKERS ON THE SIGHT.
Narrator: TO SECURE THEIR MASSIVE STRUCTURE,
GEOFFROY'S TEAM FIRST DIG OUT A 30-FOOT-DEEP FOUNDATION PIT.
THEY REINFORCE ITS WALLS WITH CONCRETE PANELS.
THEN THEY DRILL 400 HOLES 130 FEET DOWN INTO THE GROUND.
[ DRILLS WHIR ]
THEY FILL THEM WITH A CONCRETE SLURRY.
THE SLURRY SOLIDIFIES,
FORMING PILES THAT PROP UP THE BASE OF THE BUILDING.
THEY'RE JUST LIKE THE PILES UNDERNEATH SACRé COEUR.
Vauthier: BUILDING IN PARIS IS NOT SO SIMPLE.
THERE ARE A LOT OF PROBLEMS WITH THE UNDERGROUND.
THE FOUNDATIONS ARE REALLY CRUCIAL --
NOT STRONG ENOUGH, THE BUILDING WOULD CRACK.
Narrator: THE TEAM HAS CONQUERED THE SOFT GROUND,
BUT THEY STILL HAVE THEIR WORK CUT OUT.
[ SHOUTS ]
THE FIRST CONCERT IS DUE TO BE PERFORMED
IN LESS THAN 12 MONTHS.
WHEN COMPLETE, THE PHILHARMONIE DE PARIS
WILL BECOME A MODERN ICON FOR THE CITY...
...ONE BUILT IN THE MOST UNLIKELY OF SPOTS.
INGENIOUS FOUNDATION DESIGN HELPS ENGINEERS IN PARIS
EXPAND THE CITY OVER STONE THAT DISSOLVES IN WATER.
BUT MORE CHALLENGES REMAIN.
THE CITY IS BEING ATTACKED BY ANOTHER MENACE --
DEVASTATING FLOODS.
Narrator: PARIS...
A CITY PERCHED ON A MAZE OF CRUMBLING TUNNELS AND QUARRIES.
ENGINEERS RACE TO PROP UP ITS STREETS TO STOP THEM CAVING IN.
BUT THERE'S ANOTHER DEADLY THREAT
BENEATH PARIS' FAMOUS BOULEVARDS -- GROUNDWATER.
FOR CENTURIES, MUCH OF WHAT IS NOW PARIS
WAS NOTHING BUT MARSHLAND.
THOUSANDS OF YEARS BEFORE THE ROMANS SETTLED HERE,
AN ANCIENT BRANCH OF THE RIVER SEINE
CUT RIGHT THROUGH THE AREA.
THE WATER SEEPED THROUGH THE RIVERBANKS,
SATURATING THE GROUND.
AN IMPENETRABLE LAYER OF CLAY
STOPPED IT FROM DRAINING DEEPER INTO THE EARTH.
TODAY, THIS ANCIENT RIVER BRANCH
HAS LONG SINCE DISAPPEARED FROM SIGHT,
BUT ITS LEGACY IS STILL THREATENING THE CITY.
[ CAR HORNS HONKING ]
RAINFALL CAUSES THE LEVEL OF GROUNDWATER
LYING UNDERNEATH THE CITY TO RISE.
IT THREATENS TO DROWN PARIS FROM BELOW.
ENGINEERS HAVE BEEN BATTLING THIS GROUNDWATER FOR CENTURIES.
THIS IS ONE OF THE GRAND BUILDINGS
THAT HAS SUFFERED THE MOST --
THE PALAIS GARNIER, PARIS' OPULENT OPERA HOUSE.
IT'S ONE OF THE MOST STRIKING STRUCTURES IN THE CITY.
ITS WALLS CONCEAL A LAVISH INTERIOR THAT RIVALS VERSAILLES.
ITS THEATER HOSTS 2,000 PEOPLE A NIGHT.
UNDERNEATH ITS STAGE LIES A SECRET --
AN UNDERGROUND RESERVOIR.
IT HOLDS ENOUGH WATER TO FILL MORE THAN 45,000 BATHTUBS.
THE PALAIS IS ONE OF THE MOST CELEBRATED EXAMPLES
OF 19th-CENTURY THEATER ARCHITECTURE.
AND THE LAKE IN ITS BASEMENT IS UNIQUE.
IT WAS DUG OUT WHEN THE ORIGINAL ENGINEERS
HIT A PROBLEM OVER 150 YEARS AGO.
GROUNDWATER FLOODED THEIR WORK SITE
FASTER THAN THEIR STEAM PUMPS COULD DRAIN IT AWAY.
SO THE ARCHITECT, CHARLES GARNIER, DEVISED A NOVEL FIX.
Armitage: SO, THIS WAS THE SOLUTION.
A LAKE, ESSENTIALLY, BENEATH THE PARIS OPERA HOUSE
THAT EXTENDS FOR 100 METERS INTO A VAST NETWORK OF TUNNELS.
Narrator: TO SOLVE THE GROUNDWATER PROBLEM,
ENGINEERS FIRST HAD TO PUMP MORE WATER INTO THE SITE.
THIS IS CRAZY.
Narrator: THEY CONTAINED THE WATER INSIDE
THIS GIANT 25,000-SQUARE-FOOT STONE RESERVOIR.
MOST PEOPLE WOULD ASSUME THAT YOU WANT TO GET THE WATER
OUT OF YOUR CONSTRUCTION SITE
RATHER THAN BUILD A GIGANTIC SWIMMING POOL
AND THEN BUILD YOUR BUILDING ON TOP OF IT.
WHAT MIGHT SEEM AS A BIZARRE SOLUTION ACTUALLY WORKS
BECAUSE THE PRESSURE OF THE WATER
KEEPS THE GROUNDWATER BELOW FROM COMING THROUGH.
Narrator: INGENIOUS ENGINEERING
SAVES THE PALAIS GARNIER FROM FLOODS.
TODAY, PARIS' NEWEST OPERA HOUSE FACES THE SAME FATE.
OPENED IN 1989,
THE OPéRA BASTILLE BOASTS A 2,700-SEAT AUDITORIUM.
SEVEN FLOORS OF THIS BUILDING SIT BELOW GROUND.
IT TAKES FIVE HEAVY-DUTY PUMPS TO STOP GROUNDWATER
FROM SEEPING INTO THE LOWER FLOORS.
THE PUMPS DRAIN UP TO 20,000 GALLONS OF WATER AN HOUR
FROM AROUND THE BUILDING.
[ CONVERSING IN FRENCH ]
IT'S CRUCIAL THAT ALL THE PUMPS RUN AT FULL CAPACITY 24/7,
AS THEY ARE ALL THAT STANDS BETWEEN THIS MODERN MARVEL
AND TOTAL SUBMERSION.
CLEVER ENGINEERING KEEPS PARIS' TWO OPERA HOUSES FROM DROWNING,
BUT OTHER PARTS OF THE CITY ARE UNDER THREAT.
THE WATER TABLE HAS RISEN BY MORE THAN 42 FEET
OVER THE LAST 20 YEARS IN SOME PARTS OF PARIS.
SURPLUS RAINWATER IS A REAL DANGER.
RAIN FALLING ONTO SATURATED GROUND
COULD OVERWHELM DRAINAGE NETWORKS,
FORCING WATER INTO BASEMENTS AND THE STREETS ABOVE.
IF POWERFUL STORMS HIT,
THERE WILL BE NOWHERE FOR THE RAINWATER TO GO...
...EXCEPT TO SUBMERGE THE CITY.
Narrator: PARIS IS A CITY AT RISK
FROM THE VERY GROUND IT'S BUILT UPON.
COLLAPSING TUNNELS AND A FAST-RISING WATER TABLE
THREATEN TO SWALLOW THE CITY.
WORSE STILL, THE RISING GROUNDWATER
SEEPS INTO THE RIVER SEINE,
ENDANGERING BUILDINGS AND HOMES ALONG ITS BANKS.
THIS COMBINATION OF A HIGH WATER TABLE
AND A SWOLLEN RIVER IS DEADLY.
PARIS, 1910.
EXCESSIVE RAIN CAUSED THE RIVER SEINE TO OVERFLOW.
BELOW GROUND, A RISING WATER TABLE FLOODED SEWERS,
METRO TUNNELS, AND THEN THE STREETS ABOVE.
A QUARTER OF THE CITY SHUT DOWN.
A SIMILAR EVENT TODAY WOULD AFFECT 5 MILLION PEOPLE
AND COST THE CITY OVER $40 BILLION.
SO ENGINEERS MUST CONTROL THE SEINE,
AND THE FIGHT STARTS HERE -- SIAAP,
THE ORGANIZATION THAT CONTROLS THE CITY'S SANITATION
AND MONITORS THE WATER LEVELS.
Armitage: PARIS, AS A CITY, SITS ON TOP OF A LOT OF GROUNDWATER.
THAT WATER NEEDS TO BE CONTROLLED.
Narrator: THE TEAM DIVERTS EXCESS WATER
TROUGH A NETWORK OF PIPES AND TUNNELS INTO TREATMENT PLANTS.
Armitage: WHEN IT RAINS, YOU NEED TO GET RIDE OF THE WATER.
YOU NEED TO GET IT OFF THE STREETS
AND OUT OF THE GROUNDWATER AND AWAY.
Narrator: THEY HAVE ONE BIG WEAPON IN THEIR ARSENAL...
...TIMA, A HUGE STORM DRAIN.
IT'S 22 FEET WIDE AND RUNS FOR MORE THAN A MILE BENEATH PARIS.
IT'S THE LARGEST WATER-STORAGE TUNNEL IN EUROPE.
THE TUNNEL CAN STORE UP TO 21 MILLION GALLONS OF WATER.
IT ALSO CHANNELS EXCESS WATER INTO HUGE TREATMENT PLANTS.
ONCE THE STORMS PASS AND WATER LEVELS FALL,
IT FEEDS IT BACK INTO THE SEINE.
TIMA DIVERTS EXCESS RAINWATER AWAY FROM THE RIVER,
PREVENTING DEVASTATING FLOODS.
ON THE OUTSKIRTS OF PARIS
LIES A SECOND LINE OF FLOOD DEFENSE --
A HUGE RESERVOIR, ONE OF FOUR,
THAT CAN STORE UP TO 45 BILLION GALLONS OF WATER.
WHEN HIGH RAINFALL IS IMMINENT, ENGINEERS OPEN UP VAST CHANNELS,
DIVERTING WATER AWAY FROM THE SEINE
AND INTO THESE MAN-MADE LAKES.
Glasser: IF THE LAKES DIDN'T EXIST,
THE EXCESS WATER THAT WE STORE
WOULD FLOOD THE TOWN OF PARIS, OF COURSE.
[ BUZZING ]
Narrator: IT'S NOVEMBER.
THE COMING MONTHS WILL BE WET.
PATRICK NEEDS AS MUCH ROOM AS POSSIBLE IN THE RESERVOIR,
SO HE PREPARES TO OPEN A VAST OUTLET
TO DRAIN OFF EXCESS WATER.
RESERVOIRS LIKE THIS CONTROL THE SEINE...
TO STOP MOST FLOODS FROM DESTROYING PARIS.
BUT THEIR CAPACITY IS LIMITED.
Glasser: IT'S VERY IMPORTANT TO HAVE IN MIND
THAT WE CANNOT PROTECT AGAINST ALL THE FLOODS.
WE CAN STORE FLOODS WHICH CAN OCCUR
EVERY 10 YEARS OR 20 YEARS, NO MORE THAN THAT.
Narrator: SO FOR PATRICK AND HIS TEAM,
NEW PROJECTS ARE ON THE HORIZON.
A PLANNED PUMPING STATION SOUTH OF PARIS
WILL FURTHER SAFEGUARD THE CITY.
Glasser: IT'S A VERY IMPORTANT JOB.
WE KNOW THAT WE HAVE A PUBLIC SERVICE
TO THE PEOPLE TO PROTECT AGAINST FLOODS.
Narrator: THE BATTLE TO SAVE PARIS GOES ON.
FOR NOW, PARIS' CITIZENS HAVE TO PIN THEIR HOPES
ON THE INGENIOUS INVENTIONS
THAT SUPPORT ITS EXTRAORDINARY INFRASTRUCTURE
AND PROP UP ITS BUILDINGS, ANCIENT AND MODERN,
HELPING IT TO SURVIVE FOR GENERATIONS TO COME.