>> NARRATOR: One of the
deadliest natural disasters in United States history,
Hurricane Katrina devastated New Orleans-- submerging it under a
torrent of floodwater. Levees failed, and water pumping
systems below sea level were flooded.
The roof of the Superdome-- where thousands sought shelter--
was torn to shreds. And this bridge, linking the
city to outside relief efforts, collapsed like a set of
dominoes. How could it all happen?
Now "Engineering Disasters: New Orleans" on<i> Modern Marvels.</i><font color="#FFFF00">
Captioning sponsored by</font> <font color="#FFFF00">A&E TELEVISION NETWORKS
>> NARRATOR: In August 2005,</font> the close to half million
residents of New Orleans knew all hell was about to break
loose. >> PRESIDENT BUSH: I urge
all citizens to put their own safety and the safety of their
families first by moving to safe ground.
>> NARRATOR: A monster named Hurricane Katrina was
tearing across the Gulf of Mexico.
The Category 5 hurricane, packing winds of nearly 175
miles per hour, was bearing down on the city, and was predicted
to make landfall after dark. As expected, Katrina pounded
the Louisiana coastline. However, after it made landfall,
it was downgraded to a Category 4 storm with winds of less
than 150 miles per hour. And the eye of the hurricane
veered northeast-- away from the city.
>> TOBY UPSON: At the last second it made this little turn.
And we're all so excited. It's like, no we're not going to
get the brunt of the storm. New Orleans is going to make it.
We're going to make it. >> NARRATOR: Celebrations would
prove to be short-lived. By missing the city, Katrina's
ferocious winds, moving in a counterclockwise pattern over
Lake Ponchartrain to the north, and the Gulf of Mexico to the
east, sent an estimated 15-foot storm surge into the city
through its backdoor drainage canal system.
>> ELIZABETH ENGLISH: Storm surge is the swell of water
caused by the hurricane winds. And it raises the water level,
so it's as though it's a high tide that is enormously high
and just comes in fast. >> NARRATOR: Only the levees and
flood walls could protect the city from the impending
catastrophe. But in a series of engineering
disasters, the levees failed on a massive scale.
>> JOSEPH SUHAYDA: Once the breach occurred, there was a
wall of water released-- like a tsunami-- that flowed into this
residential area. >> NARRATOR: First, a levee
flood wall broke along the Industrial Canal Waterway on the
city's east side. Storm surge water rushed through
the breach into an area known as the Ninth Ward.
>> NARRATOR: Then a second flood wall on top of the 17th Street
Canal Levee suffered a two-city- block-wide breach.
This allowed the water of Lake Ponchartrain to run into the
city. Then a third levee flood wall
collapsed along the London Avenue Canal.
>> UPSON: You can clearly see how the walls come down and the
water just kind of pushed over it.
>> NARRATOR: These levees and flood wall breaks put more than
80% of Orleans Parish under water.
Thousands of victims were left stranded.
>> PRESIDENT BUSH: We're dealing with one of the worst natural
disasters in our nation's history.
>> NARRATOR: With the city submerged, New Orleans' system
of mammoth water pumps, used for more than 80 years to drain the
city, was of little use. >> GABRIEL SIGNORELLI: Our
biggest problem was water. Water rolled into the station,
rolled across the floor. The power had to be cut to them.
Water rose to this height right here.
That's it-- our pumps are shut down.
We're dead in the water, we're decommissioned, no more pumping.
>> NARRATOR: But the flooding wasn't the only disaster Katrina
visited upon New Orleans. Despite evacuations, up to
25,000 residents remained in the city.
Many fled to the Louisiana Superdome-- a structure built
on higher ground, and supposedly engineered to withstand
hurricane-force winds. However, most of its roof was
ripped apart during the storm. >> NARRATOR: Thousands were
rescued from high water-- many from rooftops.
(<i> sobbing</i> ) Getting relief to victims became
extraordinarily difficult. In another engineering disaster,
a main route into the city-- the Interstate 10 Twin Span Bridge--
collapsed as a result of the storm's massive water surge.
>> NARRATOR: The city was left with no power... scarce drinking
water... dwindling food supplies and incidents of
looting. Up to 1,300 victims did not
survive. New Orleans looked like a Third
World country. >> SALLY REEVES: It was a
really apocalyptic event for the city to flood and fires to break
out in the water. And people to be trapped in
their homes. The collapse of civilization
seeming to be imminent. >> NARRATOR: Why had New Orleans
been so vulnerable? A shocked nation began to look
for answers. >> SUHAYDA: The mystery that
we're trying to uncover, in terms of the engineering
performance of the design, is what caused the variety of
failures that we saw. Was it a strong hurricane, or a
weak design? >> NARRATOR: An army of
scientists, geologists and engineers descended on the
crippled city to unlock this mystery.
One of the so-called geo-detectives was Dr. Joseph
Suhayda... an oceanographer, geotechnical
coastal engineer and former professor at Louisiana State
University. >> SUHAYDA: Right after the
storm hit, I investigated the causes for some of the breaches
and flood wall failures that occurred.
We had to do this immediately after the storm, before any
evidence would be erased by either repairs or some natural
processes that would obscure what we were trying to look at.
>> NARRATOR: Dr. Suhayda reached the scene without a moment to
spare. The Army Corps of Engineers was
rapidly repairing the levee and flood wall breaks to protect
against further storms which could strike during the
remainder of what would turn out to be an extremely active
hurricane season. >> SUHAYDA: There were a lot of
unknown factors in terms of the levee breaches.
And so we had to look into the factors that would explain why
they failed under conditions that would appear that they
should not have failed under. >> NARRATOR: In fact, the
engineering failures may have been over 300 years in the
making... beginning when the French
arrived at the end of the 17th century.
The first settlers found a swampy area they called<i> Le
Flottant--</i> The Floating Land. The soil on which New Orleans
was built is naturally very wet, even spongy, and consists
of silt carried from the Mississippi River.
The city is mostly surrounded by water.
Only parts of New Orleans are a few feet above sea level.
Most of it is either at, or ten feet below sea level.
>> REEVES: The topography has been likened to a soup bowl
because the front... the river end is high on the rim, and the
middle is low, like the bottom of a bowl.
>> NARRATOR: Before it was known as "The Big Easy," New
Orleans was named "The Crescent City."
The French first built on the crescent-shaped high elevation
along the Mississippi River. This is where the famous French
Quarter is now located. From the beginning, the French
had problems with flooding from the Mississippi River.
So they began to build a system of levees.
A levee is an earthen dam that runs along a waterway.
>> REEVES: The levee system goes literally to the founding of New
Orleans. I would say at the very, very
latest, 1720-- and possibly 1718.
>> NARRATOR: After the Louisiana Purchase in 1803, The United
States took control of the city. As it grew, the swampland below
sea level was converted into farmland.
During the next hundred years, some 350 miles of levees were
built to protect this new land. >> SUHAYDA: Individual
landowners-- plantation owners-- were responsible for building
and maintaining the levees. So it was a very private-based,
non-governmental type of action. >> NARRATOR: The dirt that
comprises the base of the levees is that soft, spongy Mississippi
Delta soil. >> SUHAYDA: What we have here is
an example of a delta soil, in terms of its characteristics
of having high organic content, being very, very weak, having
high clay content. >> NARRATOR: In 1927, the United
States Army Corps of Engineers took control of the levee
system. The Corps widened many of the
levees and built them higher. But as the system was
strengthened, there was another problem.
>> SUHAYDA: New Orleans in the metropolitan area is sinking,
because of the geology of the soils beneath the city.
The water that's in the material is being squeezed out, and so
the surface has been moving down and will continue to move
down for hundreds of years. >> NARRATOR: This sinking is
known as "subsidence." It's caused by the reclaiming of
swampland. When water and mud were pumped
out, the area began to fall even further below sea level.
Subsidence at one time had been balanced by sedimentation--
new silt, sand and clay deposited when the Mississippi
River flooded. But since the levees were
constructed, the river has been controlled and sedimentation has
stopped in New Orleans. >> SUHAYDA: The estimates vary
for the sinking rates, but we have them as high as one inch a
year. The typical being about a half
an inch a year-- of actual sinking of the surface downward
over time. >> NARRATOR: Even at a rate of a
half inch per year, the city will subside or sink more than
four feet in a century. For decades geological experts
warned of the peril of this sinking city, and the fragile
levee system that protected it. >> SUHAYDA: This was a disaster
waiting to happen, because we knew there were hurricanes
that could flood the city with the protection that we had.
>> NARRATOR: Dr. Suhayda was determined to find the failures
that caused the levees to break. The evidence he was about to
uncover would provide the first clues to how this engineering
disaster could have occurred. "Engineering Disasters: New
Orleans" will return on<i> Modern</i> <i>Marvels.</i>
>> NARRATOR: We now return to "Engineering Disasters: New
Orleans" on<i> Modern Marvels.</i> Weeks after Katrina wreaked
havoc on New Orleans, the city remained mostly underwater.
The critical question-- why did the levees fail?
Did Katrina overwhelm the city's flood defenses, or did faulty
construction cause them to burst open?
>> RICHARD WAGENAAR: The levees and flood walls were built to
what we refer to simply as a Category 3 fast-moving storm.
>> NARRATOR: The National Hurricane Center classifies
hurricanes according to wind speed and storm surge.
The scale ranges from the least- severe Category 1 hurricane,
with winds of 74 to 95 miles per hour and a storm surge of four
to five feet, to the most destructive Category 5, where
winds soar to more than 155 miles per hour with a storm
surge of higher than 18 feet. >> WAGENAAR: Well, we started
the Hurricane Protection Project back after Hurricane Betsy in
1965. >> NARRATOR: Katrina wasn't
the first hurricane to devastate New Orleans.
In 1965, Hurricane Betsy, a Category 4 storm with winds of
125 miles per hour, hit New Orleans dead on and plowed
through the outdated dirt levee system, flooding the Ninth Ward
and killing 75 people. Although Betsy caused less
damage than Katrina, there was an effort to ensure that this
would not happen again. The U.S. Congress gave the
Army Corps of Engineers the responsibility of building
concrete flood walls on top of the seven-foot-high levees to
give the city more protection. They're known as "I" walls.
One-inch-thick steel sheet pilings were driven 20 to 25
feet underground to secure the base.
Tied to them, reinforced concrete walls six inches thick
were built on top of the dirt levees.
However, the Army Corps constructed only eight-foot-high
flood walls on top of the levees, for an average total of
about 15 feet of protection. These could contain only a
Category 3 hurricane storm surge.
To fully protect the city against a Category 5 storm
surge, critics warned higher flood walls should be
constructed. >> WAGENAAR: The Army Corps of
Engineers in New Orleans was only authorized to build a
Category 3 protection-type system by the Congress of the
United States. A Category 5 would have required
different authorizations and an extremely high amount more of
funding. >> NARRATOR: Katrina was a
Category 4 storm with an estimated surge of more than 15
feet. Geo-detective Joseph Suhayda
uncovered evidence suggesting one flood wall failure was
caused by the action of the water over-topping it.
This occurred on the east side of the city at the Industrial
Canal. >> SUHAYDA: It was a condition
like this where the water would come over the top of the flood
wall and actually plunge down and scour at the base.
And here below me you can see what is remaining of the pit
that was scoured out by the flowing water.
And that scouring action would continue as long as the water
kept flowing over the top of the flood wall.
>> NARRATOR: Scouring occurs when flood water pours over a
wall like a waterfall. The force of the falling water
from the top of the flood wall scours, or digs out the dirt
along the wall's foundation, undermining it and causing the
entire wall to collapse from top to bottom.
>> SUHAYDA: After the breach occurred, there was a wall
of water released beneath hundreds of thousands or
millions of pounds of force. >> SIMMONS: The wall of water
was unbelievable. They had cars and everything
washing down, taking everything in its path, cars and everything
popping up from the surface and everything.
I never seen nothing like that in my life.
It was unbelievable. >> NARRATOR: Ninth Ward resident
Palozzolo Simmons lived just a few blocks from the Industrial
Canal Levee when it failed. His home was totally destroyed.
>> SIMMONS: I was right inside of here when that storm come
through here, and I could not been here talking to y'all.
Could have been dead. The water was so deep I had to
swim from one rooftop to another rooftop.
I was stranded here for three days.
Three days with no rescue help whatsoever.
I got out of this area. A guy came in with a boat,
rowing a boat. He seen me and he came and
picked me up. >> NARRATOR: Palozzolo Simmons
was lucky. He survived.
In his Ninth Ward, which was hit hardest by the storm surge,
miles of homes were destroyed. >> NARRATOR: We now return to
"Engineering Disasters: New Orleans" on<i> Modern Marvels.</i>
more insidious culprit caused the massive failures on both the
London Avenue Canal and the 17th Street Canal, the very building
material of the levees themselves-- the soil.
>> SUHAYDA: As we can see here, the flood wall is in place.
It's vertical, it's got a nice clean edge.
We don't see any of the breaking or bending that occurred
in the Industrial Canal. And that's because the mechanism
of failure was different. In this case, the soils that
were holding up the flood wall were saturated by the storm
surge, weakened and failed and then slid and raised up, pushing
that soil mass into flood walls into the homes.
>> NARRATOR: This is known as "heaving."
As Katrina's storm surge filled the canal, water pressure rose
in the soft delta soil underneath the flood walls.
When the rising pressure and moving water overcame the soil's
strength, it suddenly shifted, taking surrounding material and
the flood walls with it. >> SUHAYDA: This is an
extraordinary situation here. What we have is a piece of the
original soil that was holding up the flood wall that was about
40 feet to my right, right along the 17th Street Canal.
So this material here was actually alongside the channel
at one time. It got displaced and lifted
upward. This fence was slightly outside
the area of the flood wall. So we've seen a movement and an
uplifting of the soils by about 40 feet.
>> NARRATOR: This movement might have been prevented if another
engineering failure had not occurred.
The steel sheet-pile bases driven 20 to 25 feet underground
gave the flood walls insufficient support.
A deeper sheet piling would probably have anchored the
flood wall in much stronger soil.
>> SUHAYDA: If the soil movement takes place below the
bottom of that sheet pile, then the sheet pile is really passive
and doesn't protect from the soil motion.
And that's what happened at the 17th Street Canal.
But if the soil is strong enough, then the sheet pile
actually holds up the concrete wall.
>> NARRATOR: Along the London Avenue Canal, the Army Corps
of Engineers is repairing the flood wall breaches with
deeper steel sheet pilings. Perhaps they'll prevent a
catastrophe of this kind in the future.
>> UPSON: These are the old sheet piling underneath the
flood wall. The new sheet piling we're
driving are 79 feet are these big ones right here.
And these are the old ones which are 22 feet.
It's a much stronger sheet-pile section than the old sheet pile.
>> NARRATOR: Another repair the Army Corps has undertaken is the
replacement of the old "I" walls with what are known
as "T" walls. The flood wall is secured with
a concrete base embedded underground.
Attached to the base are steel sheet pilings of up to 70 feet
deep. >> UPSON: So you have a lot of
capacity in these piles where they can't be moved so the wall
can't turn as long as those piles are there.
>> NARRATOR: Although the damaged levees are being rebuilt
by the Army Corps, they still will only withstand a Category 3
storm surge. There are no plans to heighten
the flood walls to protect against a Category 5.
>> WAGENAAR: The estimates: it would take many, many years.
Five to ten years at least. Uh, dollar estimates range in
the 20-plus billion-dollar range just for New Orleans area.
>> NARRATOR: However, Dr. Joseph Suhayda believes even if the
flood walls were built higher, that wouldn't take into account
the soil uncertainties, raising questions about the
design of the entire levee system.
>> SUHAYDA: The analogy can be made that when you have very
soft soils, even if you have a very strong structure on top of
that, then the whole structure is going to fail, somewhat like
if you put bricks on Jell-O. The bricks can be very, very
strong, but it's the strength of the Jell-O that really
determines whether the bricks are going to move.
One of the solutions to the problem of minimizing the threat
associated with flood walls is to build floodgates at the
northern end of our drainage canals, and therefore keep the
storm surge from coming into the drainage canals and from
threatening the flood walls. >> NARRATOR: Floodgates are
enormous walls that can be raised or lowered by hydraulic
systems to regulate water flow. The Army Corps is looking into
the possibility of placing floodgates at canal openings.
>> STAN GREEN: The gate would be raised above the level of the
water so the water would gently pass beneath it.
In the event a storm was approaching, the gate would be
lowered so that it would block the flow of water.
>> NARRATOR: Rebuilt levees, flood walls and floodgates could
constitute New Orleans' first line of defense against another
hurricane catastrophe that might help protect New Orleans'
second line of defense, a system of 24 water pumping stations
that flooded after Katrina and left New Orleans crippled for
weeks in a polluted swampland. >> NARRATOR: We now return
to "Engineering Disasters: New Orleans," on<i> Modern Marvels.</i>
For more than two weeks after Katrina hit, New Orleans
remained underwater. The city has one of the world's
largest water pumping systems, capable of pumping 30 billion
gallons a day. But because the levees failed,
the pumps, located below sea level, became inundated with
floodwater. >> GABRIEL SIGNORELLI: The
water's coming in, first time ever.
Electricity and water don't mix. Operator shut the station down,
shut the motors off and de-energized.
>> NARRATOR: Not only were the electric pumps immobilized, pump
workers literally had to swim for their lives.
>> WALLACE RAINEY, JR.: At that point, I had just survival going
through my mind. I wanted to live.
We were all scared. >> NARRATOR: Pump station
attendant Wallace Rainey had to swim in 20-foot-deep floodwater,
to reach a stable place, before being rescued.
>> RAINEY: This is where we stood as the waters was rising.
It was coming in through the windows; the windows was broke.
Had water coming across the tops of the pumps; it was
lapping at our feet. We were pretty scared.
We didn't know if we were going to make it through that day.
>> NARRATOR: The men who constructed the pump stations
could never have imagined the catastrophic flooding scenario
that followed Katrina. For centuries, New Orleans had
attempted to deal with water accumulation problems.
But it wasn't until 1912, when Albert Baldwin Wood invented a
successful screw pump, that the city found a solution.
Remarkably, many of Wood's screw pumps, over 80 years old, are
still in use today. The pumps work on a very simple
principle: Encased in a sealed cast-iron drum, air is
transferred out, creating a vacuum inside.
The water is sucked in by the vacuum, and a 14-foot-diameter
screw-- or propeller-- turning at 83 rpm, propels the water
out. It wasn't the actual pumps, but
rather the electric synchronous motors which supply the power,
that were affected by the flooding.
The motors are exposed to the elements and positioned in
pits, partially below the floor. >> WARREN REINE, JR.: The
water got approximately this high on this pump.
And when water hit electricity, boom!
Basically, you have no more operations.
>> NARRATOR: It took weeks for the water to be pumped out of
the stations and the motors to thoroughly dry.
Then another problem caused even more delays in getting the pumps
back on line. >> SIGNORELLI: We look at this
station-- and a lot of our other facilities-- as working in an
actual museum, because you could look at these pumps and motors
and they are extremely old. There's no manufacturer to go
back to for these particular parts.
So you're looking at either fabricating them ourself,
yourself, or going to another fabrication shop to have that
done. >> NARRATOR: The city's sewerage
and water board is preparing its pump system for future flooding.
Already, there are a few prototypes in place to shield
and protect the pumps' electrical motors.
>> FREDERICK S. YOUNG: After the hurricane, the water was
approximately here. It inundated this pump.
Over at this pump, the water didn't get into the workings of
the pump-- it's called a sealed pump.
This pump was able to be started when we got here.
This is a possible solution for a situation-- if we ever
have it again-- that's as traumatic as this storm
flooding the city. >> NARRATOR: Another remedy is
to elevate the entire electric system, which runs the pumps.
This has already been accomplished at one station.
>> YOUNG: Some of this equipment is in the basements of
some of these pumping stations. That equipment possibly needs to
be higher, so that if we do get a situation where we need the
pumps, and there's a lot of water in the city, that this
equipment stays dry. >> NARRATOR: It took 21 grueling
days to pump out New Orleans. But if the pumps hadn't been
flooded, would the city itself have stayed above water?
>> G. JOSEPH SULLIVAN: If our drainage pumping station had not
been damaged, and the levee breach could be stopped in its
early stages, it would take 12 to 20 hours, possibly, to pump
out what ran in during that time.
>> NARRATOR: Instead, standing floodwater left the city in an
uninhabitable soup. Thousands sought shelter in
the New Orleans Superdome. But another engineering disaster
would make this shelter of last resort a living nightmare.
"Engineering Disasters: New Orleans," will return, on<i>
Modern Marvels.</i> >> NARRATOR: We now return to
"Engineering Disasters: New Orleans," on<i> Modern Marvels.</i>
With thousands of survivors left stranded in floodwater, the
Louisiana Superdome became a shelter of last resort.
>> DOUG THORNTON: This is a football stadium.
It's not a hospital, it's not a hotel.
We're equipped to handle people for four hours, not four days.
>> NARRATOR: Conditions deteriorated rapidly after
Katrina's 145-mile-per-hour winds ripped apart the
Superdome's nine-acre roof. >> TRAHAN: Hurricane-force
winds began to cut, pierce and slice this roofing system,
resulting in something similar to an onion, beginning to peel
back the layers. First the membrane, then the
insulation, then the structural deck.
>> NARRATOR: Inside the Superdome, rain pouring in from
the damaged roof shorted out the main electrical system.
The dome had to depend on a back-up generator.
>> THORNTON: It was like living an epic disaster film.
It was, uh, it was an unbelievable experience.
There's minimal lighting, there's no air conditioning, and
it's just a matter of time before you lose water pressure.
You have, you know, 15 to 20... 25,000 people, eventually, in
your building using the restroom with no water pressure, you can
imagine what that's like. So we lost the toilets and the
ability for people to use the facilities in here, after a
couple of days. Constructed in 1975 the 1.9
million square foot indoor stadium was one of the first
sports domes of its kind. The stadium itself covers 13
acres. It reaches 27 stories at its
peak and encloses a volume of more than 125 million cubic
feet. Some 20,000 tons of steel and
150,000 cubic yards of concrete were required for its
construction. >> THORNTON: And certainly the
Superdome was built to the code at that time in 1975.
The building, structurally, is very sound, uh, so, yes, it was,
it was built to withstand hurricane-force winds.
>> NARRATOR: Why then did the roof fail when subjected to
Katrina's winds? The engineering disaster
involved, not the structures roof itself, but rather the
surface that covers the roof.
>> THORNTON: It's a rubber membrane over a two-inch
Styrofoam based material that is laid over a metal deck, and we
lost one of the apex vents, one of the exhaust dampers at the
very top, very apex of our roof, 270 feet above the floor.
>> NARRATOR: The exhaust dampers are housed in five-foot-high,
20-foot-long box structures resting on the roof's surface.
When the hurricane winds blew one of the dampers off the roof,
the resulting breech exposed the rubberized roof membrane.
It began to tear. Once this occurred, the winds
were able to move under the membrane seal and shred it piece
by piece. >> TRAHAN: The effect on this
roof was the removal of almost 70% of the membrane itself,
exposing all of the structural metal deck and opening up the...
holes into the roof itself. >> NARRATOR: The Superdome roof
would have to be rebuilt. By November 2005, the roof had
been covered with a thin, temporary hardened foam surface.
>> TRAHAN: But now we're gonna move to a long-term solution.
A long-term solution of a galvanized structural deck with
a new foam roofing system. Hopefully, we'll protect the
dome better than ever. It will result in a better
system, a deck that will resist the inevitable next hurricane.
>> NARRATOR: However, in that desperate week after Katrina,
there was another engineering disaster impacting the thousands
in the Superdome and across the city.
The Interstate 10 Twin Span Bridge across Lake Ponchartrain
collapsed because of the hurricane storm surge.
Since this was one of the main routes into the city, relief
supplies were difficult to deliver.
>> MARK LAMBERT: The tremendous force of nature and the awesome
power that unleashed on this bridge, is something that you
just had to see to believe. When you're looking at these
265-ton concrete segments just being tossed around like toys...
>> NARRATOR: The Twin Span Bridge was constructed in 1964,
linking New Orleans with Interstate 10.
It's a concrete structure spanning 5.4 miles of Lake
Ponchartrain. The bridge consists of
approximately 460 concrete segments, each weighing about
265 tons. The segments are held up by
pilings that are sunk 100 feet into the lake bed, but rise less
than 10 feet above the lake surface.
The pilings withstood the storm surge, but because of a design
flaw, some of the girders supporting the concrete segments
did not. >> LAMBERT: Under this bridge
span right here, the tidal surge came up and it reached probably
about to the top of this girder, or right around there.
It trapped air between these girders and that caused about a
million pounds of pressure that shoved up on this concrete
segment. At about the same time, you've
got probably about three- quarters of a million pounds
of pressure from a tidal surge that's hitting the side of this
segment. So all of that combined to just
shove this segment up and out, and it just kind of tossed it
into the lake like it was a domino.
>> NARRATOR: A total of 435 segments of both spans were
damaged, making the bridge impassable.
Because this passageway is critical to the city, it needed
to be rebuilt as soon as possible.
It took just 17 days to repair one of the spans.
>> LAMBERT: What we had to do was cannibalize segments from
one span and put them on the other span so that we could
establish two-way traffic on one span.
That left us with huge gaps in the remaining span, and what we
did is we used bridge panels that we attached to the current
structure, basically made of steel, galvanized steel.
So instead of replacing those missing spans with other
concrete spans, we put in these bridge panels.
You can see with this new truss system and with these, uh,
panels, uh, there's really no place for any significant air
pressure to build up, so, uh, it's really not going to be
susceptible to the same kind of air pockets and air pressures
as the concrete panels were. So that's one way that you can,
uh, fix this. >> NARRATOR: By early January,
2006, both sides of the Twin Span Bridge had been rebuilt and
opened to traffic. However, these are just short-
term repairs. >> LAMBERT: The long-term
solution to this is to build an elevated bridge, at least twice
as high as the current bridge. Uh, we want to make sure that
it's not susceptible to that kind of tidal surge.
We believe that kind of bridge would cost about $600 million,
but we believe it would be worth it to ensure that this
(<i> sax plays</i> ) On Bourbon Street, the neon
lights are flashing and the booze and jazz are flowing.
The Big Easy is making its best effort to come back.
But the French Quarter is located on the city's highest
ground and received the least amount of flood damage.
Beyond it, vast areas of the city have been extensively
damaged. To fund what is likely to be the
largest demolition and rebuilding project in America's
history, the mayor of New Orleans is asking for
tens of billions of dollars in federal aid.
>> RAY NAGIN: We are working very feverishly with banking
institutions, with financial folk, as well as federal
officials to secure a line of credit that will sustain us.
>> NARRATOR: But there is a looming, potentially cataclysmic
crisis that may doom recovery efforts in New Orleans.
>> ROY K. DOKKA: Eventually, what's going to happen is that
the coast of Louisiana is going to be inundated by the
Gulf of Mexico. >> NARRATOR: Dr. Roy Dokka, a
professor of civil and environmental engineering at
Louisiana State University, is now using high-powered global
positioning satellites to develop true elevation points in
the state. >> DOKKA: Well, this is a GPS
measuring device. This is the antenna up here.
What we're using this for is to figure out exactly how high
we are above sea level, but more importantly, how low we
are below sea level. And what that's been able to do
is that-that, it's shown us that the sinking is occurring much
faster than what people had thought before, and it's
occurring in places that we didn't know it was happening.
>> NARRATOR: Dr. Dokka's results indicate the elevations of some
areas have dropped as much as two feet since they were last
surveyed in 1970. And the sinking continues.
According to some estimates, within the next 70 years, about
15,000 square miles of land in Southern Louisiana, known as
the wetlands, could be under water.
The wetlands encompass a marshy region that acts as a buffer
zone, slowing down hurricanes before they reach New Orleans.
>> DOKKA: We're losing, on average, a football field every
hour. >> NARRATOR: The reason for the
sinking is an ecological Catch 22, arising from human efforts
to protect against flooding from the Mississippi.
>> DOKKA: In order to stop the flooding, we levied the rivers.
We kept the river within its bank, we tamed it.
But in the process, we also disrupted the natural system.
Before, the river would naturally fill up areas that
had subsided, and as it filled them up above sea level, higher
and higher, the river then would find another course and begin to
fill up other areas that had fallen below sea level.
>> NARRATOR: In addition to the wetlands, Louisiana's other
natural defense against hurricanes has been the Barrier
Islands, which were part of the region's shoreline just a
century ago. Katrina blasted right through
them with Category 5 force. >> ELIZABETH ENGLISH: After
Katrina, uh, there's not much left of the Barrier Islands,
particularly the ones that have been protecting New Orleans.
Much of them has been washed away.
When the Barrier Islands become diminished or disappear,
then there's not that impedance there to slow the action of the
hurricane down. >> NARRATOR: Perhaps it was a
fundamental design disaster to build the city of New Orleans
on this land. Authorities are faced with an
increasingly complex decision-- whether to invest enormous
amounts of time and money to attempt to completely protect
the city with a newly designed and engineered levee system, or
to simply patch and rebuild the existing system.
>> DOKKA: This is not just a New Orleans problem, but it's an
entire coastal problem, and that means what we need to do is to
build some sort of structure that's gonna keep the water out,
building a levee that might span the entire coast.
This would be the biggest engineering project in the
history of the Earth. This would make the pyramids
look like nothing. And so what we need to do is
to start new ways of thinking, start thinking about building...
the Great Wall of Louisiana. (<i> sax playing</i> )
>> NARRATOR: But whatever the decision, the outcome for New
Orleans may ultimately lie in the unpredictable hands of
Mother Nature, and her power to transform the Big Easy into a
modern day Atlantis.
