- 9 months ago
Episode of NOVA about the collapse and reconstruction of the Key Bridge in Baltimore
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00:00March 26th, 2024.
00:12A heavily loaded container ship careens out of control
00:16and heads straight toward one of the supports
00:19of the Francis Scott Key Bridge in Baltimore.
00:22C-13, dispatch.
00:29The whole bridge just fell down.
00:31The whole bridge just collapsed.
00:33Key Bridge is down, several vehicles in the water.
00:36It's a race to find survivors.
00:38You're bringing the victim in now.
00:40OK.
00:42And remove the 50,000 tons of debris
00:46that completely cut off this vital port.
00:50People are looking at us and saying,
00:52what's the plan?
00:54The scale of the salvage operation is daunting.
00:57They need to reopen this crucial shipping route
01:00as quickly as possible.
01:02You could instantly feel the ripple effects
01:04on our economy, on Baltimore.
01:08We knew that it was going to be very dangerous, very complex.
01:12You'll certainly make your hair stand up
01:13on the back of your neck, seeing the seal drop
01:16as you're making cuts.
01:18Investigators scramble to uncover what went wrong.
01:21Asking, how did a modern ship suffer such a catastrophic loss
01:26of control?
01:27And why did a single point of impact cause the entire bridge
01:31to collapse?
01:32The problem you have is that ships have gotten bigger and larger,
01:35and the infrastructure has not kept up with them.
01:40An estimated 2,500 US bridges remain at risk of ship strikes.
01:46This could have been prevented.
01:49As vessels grow in size, can our infrastructure handle it?
01:55Baltimore Bridge Collapse, right now on NOVA.
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02:27The Port of Baltimore, Maryland is one of the busiest ports on the East Coast, and its history
02:30is as long and storied as the United States itself.
02:54So much of Baltimore's identity is actually wrapped up in its port.
02:59The Port of Baltimore has been one of the earliest trade points for not just the state
03:03before this country.
03:04I mean, that port is our economic heartbeat in the state of Maryland.
03:11Every year, it handles cargo worth more than $80 billion and supports more than 20,000 jobs.
03:22The Port of Baltimore supplies the nation with critical goods from food to pharmaceuticals.
03:30The Port has 17 separate terminals for container operations, cruise ships, and bulk cargo.
03:382,000 vessels dock here every year.
03:41It can handle some of the world's largest ships, each carrying more than 15,000 containers.
03:49To reach the port terminals, all ships must pass under the Francis Scott Key Bridge, which
03:55carries four lanes of road traffic 1.7 miles across the bay.
04:01The ships must negotiate a narrow shipping channel that runs between the main supports of the
04:06bridge.
04:11From a practical perspective, the key bridge gets you to the Port of Baltimore.
04:17But it's so much more than that.
04:19It's our skyline.
04:21It's a lovely backdrop for Baltimore.
04:30In the early hours of Tuesday, March 26, 2024, 12 ships are docked in the port.
04:38At 12.36 a.m., one sets sail for Sri Lanka with 21 crew and two local pilots onboard.
04:47It's called Dali, a 124,000-ton, 947-foot-long ship.
04:56It's part of a modern class of ships, so massive that only certain ports have channels deep enough
05:02to allow them to pass.
05:05The vessel is almost full, laden with nearly 4,700 containers, carrying everything from soybeans
05:13to perfume.
05:15But as the ship approaches the bridge, there's a sudden loss of electrical power.
05:22The ship is plunged into darkness.
05:26At 1.26 a.m., one of the pilots onboard sends out a distress call, which alerts the police.
05:32We had workers on that bridge.
05:47These are people who are fixing potholes.
05:50They were fixing potholes while we slept.
05:51Just make sure no one's on the bridge right now, that there's a crew up there.
05:57You might want to notify whoever the foreman is, see if we can get them off the bridge temporarily.
06:05Once you're good here, I'll go, Brad.
06:07The worker's on the key bridge, and then stop the outer loop.
06:11But the police are unable to reach the workers in time.
06:14C-13, dispatch.
06:25The whole bridge just fell down.
06:27The whole bridge just collapsed.
06:28C-13, dispatch.
06:33C-13, dispatch.
06:36The whole bridge just fell down.
06:39The whole bridge just collapsed.
06:41My chief of staff, he sent me a note saying, I just sent you a video.
06:48The video was of the bridge collapsing, and it literally took my breath away.
06:54It just didn't look real.
07:01We knew that one of the most tragic moments in our state's history had just occurred.
07:07That's the key bridge, key bridge.
07:10Yeah, it is.
07:11Wow.
07:14The container ship Dolly has smashed into and destroyed the bridge.
07:21Immediately, Coast Guard and police search teams race to the scene.
07:28The whole bridge is collapsed, and the bridge is sitting on top of the container ship.
07:37We started searching almost instantaneously, because our station was very close.
07:42Can you just get us near where the other fire department assets are out there?
07:47You got it.
07:48Key bridge is down.
07:49Key bridge is down.
07:50It was last reported at least several vehicles in the water, with several people still unaccounted
07:55for it.
07:56It was nighttime.
07:58It was a fairly clear night, though, so they could see.
08:01They had visibility.
08:02They had lights as well.
08:04Hey, what's going on, man?
08:05We got one out of the water.
08:07Okay.
08:08There was one survivor that went into the water in his vehicle, and he was clinging
08:14to a piece of debris when he was picked up.
08:17You're bringing the victim in now.
08:19Okay.
08:20Incredible that somebody would survive that fall and be rescued.
08:26It gave hope to the rescuers that we were going to find other victims as well that survived
08:33the fall.
08:34For your 43, sir, I have nothing at the moment.
08:37The search teams have rescued one construction worker, but six are still missing.
08:46First light reveals the full scale of the disaster.
08:56Got it.
08:58Natural water command.
09:00The dolly had so much momentum, it completely destroyed one of the main support piers that
09:06pulled up the key bridge.
09:07The ship has run aground and is trapped by the wreckage.
09:13Almost 3,000 feet of the crossing have collapsed into the Patapsco River.
09:18We've got some investigators on board.
09:20We'll be in the area of the bridge.
09:23Fortunately, the dolly's crew is unscathed, and the hull has not been breached.
09:32But no ships can get in or out of the port of Baltimore.
09:3650,000 tons of debris completely blocked the main shipping channel.
09:42The port is shut down.
09:45As the day ends, there's still no sign of the six missing workers.
09:55I remember speaking with the person who was running the operations from the Coast Guard.
10:00And I said, what is the probability that we're going to find someone alive at this point?
10:06And the answer that he gave was, Governor, my professional assessment is zero.
10:10There's a zero percent chance.
10:15I remember one of the family members who said,
10:18Quiero el cuerpo, which is, I want the body.
10:40There's a zero percent chance.
10:41There's a zero percent chance.
10:42There's a zero percent chance.
10:43There's a zero percent chance.
10:44There's a zero percent chance.
10:45There's a zero percent chance.
10:46While the search for lost workers continues, the city begins to grapple with the sheer scale
10:52of the problem.
10:53Never seen anything of that magnitude before.
10:59We had the bridge collapse with the vessel, everything mangled up on top and around.
11:08You had these big, large spans that were just laying in the water.
11:19You see four inch steel that's been bent.
11:23Bent.
11:25How can you even start to think about the force?
11:31People are looking at us and saying, what's the plan?
11:34The stakes are high.
11:36Every day the port is closed costs $15 million in lost revenue.
11:41And more than a thousand containers a day cannot move in or out.
11:47There are fears the closure could impact the wider economy, affecting commerce across the country.
11:54The U.S. Army Corps of Engineers and the U.S. Coast Guard bring in the Navy and three specialist salvage teams.
12:03The number one priority was recovering the missing personnel.
12:10The number two priority was opening the channel.
12:14The situation calls for a rapid response of unprecedented scale.
12:20The team must free the dolly from the 5,000 ton bridge section that pins down its bow.
12:27So they can tow the vessel away.
12:30But before they can fully reopen the port, they must also cut the collapsed sections of bridge into smaller pieces and lift them from the river.
12:3950,000 tons of mangled steel and concrete.
12:43It's a huge challenge.
12:48And you just think, how?
12:50How are we going to?
12:52Seeing it on the news, seeing it in photos, I was not prepared to see it, you know, up close and personal.
13:04Robin Bianchi is part of a salvage team brought in to clear the bridge wreckage from the main shipping channel.
13:11This is going to be a hell of a cleanup.
13:14And it was just so unfathomable, the amount of damage and wreckage and how massive everything was.
13:22And we instantly knew, well, we can't make any plans on how to raise this wreckage out of the water until we know what it looks like under the water.
13:31The salvage team's first task is to send divers down into the mass of twisted steel.
13:38They must try to make sense of how the mangled beams and smashed road are positioned on the riverbed.
13:46It's a key step before they can make a plan to disassemble the tangled structures safely.
13:53They're entering a very inherently dangerous situation.
13:58You have the hanger. Go back to the hanger part.
14:01Like, there was no visibility, so I kind of compared it to a metal jungle gym underwater, right?
14:08You have this rusty metal jungle gym that was plopped into zero visibility.
14:12You turn off all the lights in the room and try and tell me all the pieces of where they connect of that metal jungle gym.
14:19Oh, and by the way, the jungle gym's completely twisted and looks nothing like it did when it was built to perfection.
14:25How far are you from the first gusset that you just left?
14:29Maybe about six foot.
14:32Okay.
14:33You want to really meticulously guide them through.
14:36All right, when you have your hand on this section, we're going to call this Section J.
14:41So I'd have them mark it with a little underwater marker, and that correlated to Section J on this specific engineering plan.
14:49Can you see the other side of that pendant? Is it disconnected?
14:53Yeah, it looks still connected to a beam, like a truss.
14:58We were able to kind of map out what it looks like underwater.
15:02You verify and validate with comms, and then you move on to the next objective.
15:07So how much do you have exposed from the mud line to the top of the gusset plate?
15:13It was very dangerous for divers because you turn left and you went underneath something, like a piece of rebar that's sticking out.
15:22You have to remember that that's where you have to come back down, otherwise you could become trapped.
15:27Everything that could make diving more difficult, it was on this job.
15:34Visibility is no more than one or two feet.
15:39To give the divers a clearer picture, the team deploys underwater drones equipped with sonar to map the wreckage.
15:49Together with the hands-on dive surveys, these scans will help the team decide where to cut and lift each section of debris.
15:58This volumetric sonar uses very precise location data from various scans to essentially stitch together multiple scans to create a 3D model.
16:13The picture spoke a thousand words.
16:16It just gave a really high fidelity view of exactly what everyone was dealing with on the bottom.
16:22Down at the bottom is where you had a big mangled mess, especially in the center of the channel.
16:29Not just the steel, but the reinforced concrete from the road bed.
16:33We didn't realize until we were able to get some 3D imagery of just how catastrophic the collapse was.
16:43While the salvage teams prepare their work plans, the National Transportation Safety Board begins an investigation to answer the questions.
16:52What caused the ship to lose power and collide with the bridge?
16:56And why did the structure collapse so catastrophically?
17:09Investigators board the dolly on the day of the accident.
17:12They document the scene and meticulously gather physical and electronic evidence.
17:19They interview the captain and 20 crew, all of whom remain on the ship because of visa restrictions.
17:27They retrieve the ship's voyage data recorder, which stores audio from the dolly's bridge and details engine and rudder commands.
17:37Marcel Meuse is the investigator in charge of the dolly accident.
17:44We're looking at different aspects of the incident to answer how do we stop ships from losing power.
17:52Assuming that we can't stop ships from losing power, how do we stop them from hitting things?
17:57Assuming we can't stop ships from hitting bridges, how do we stop them from falling down?
18:01To answer this question, the team must study the structure of the bridge to understand how it collapsed.
18:08The critical structural element that allowed the key bridge to reach all the way across the river was its massive truss,
18:20a lattice of steel beams arranged in triangles that made it light yet strong.
18:30Spanning 1,200 feet, it was the third longest continuous bridge truss ever constructed.
18:37But at this extreme length, it would have buckled under its own weight without support.
18:44It needed two large reinforced concrete piers to hold it up, dividing it into three shorter spans.
18:54The key bridge was a feat of structural engineering, but it had a fundamental weakness.
19:01If you take away a critical element, you lose that equilibrium and the structure is going to collapse.
19:10With one of the main support piers destroyed, the bridge cannot span such a distance and begins to break apart.
19:19This two span becomes one span for which this bridge was not designed.
19:25You can see separation happening at the bottom.
19:28The collapse is progressing actually.
19:31And that part is going to separate.
19:36And you can see it's breaking off because of that tension.
19:41Without the rest of the truss to hold it in tension, the remaining span becomes unbalanced and collapses under its own weight.
19:50A typical progressive collapse scenario.
19:54Let's take a test run on this bridge right now.
20:10When the Francis Scott Key Bridge was opened in 1977, a failure on this scale must have seemed impossible.
20:20But back then, the largest container ships were less than half the size of the Dali.
20:27So the main piers of the key bridge were built with concrete and timber fenders, designed to absorb the impact of ships at the time.
20:37There's no way that it could have envisioned that it would be a 100,000-ton ship striking the bridge.
20:46So I've just completed the maiden voyage for News Watch 2 across the Francis Scott Key Bridge.
20:52And starting Wednesday at 10 a.m., you'll get your chance.
20:56We move more goods today than at any time in our history.
21:03The problem you have is that ships have gotten bigger and larger, and the infrastructure has not kept up with them.
21:09Lifespan for bridges is about 75 years.
21:14Ships, on the other hand, can last anywhere from 20 to 30 years.
21:20And so two to three different generations of ships can happen during the lifespan of just one bridge.
21:26Infrastructure can't change as fast as shipping can change.
21:31The force from the Dali was huge. It was a huge, huge force.
21:40The ship's enormous mass acts as a multiplier of its velocity to devastating effect.
21:49There's truly no bridge that I know that would be designed for 34 million pounds of impact force.
22:00So it's not surprising that it went down.
22:04What is surprising is that there was no protection of those peers.
22:08This could have been prevented.
22:18Five days after the collision, four construction workers are still missing.
22:23Eleven ships are trapped in the port.
22:29Many more, unable to get into the port, are diverted as far south as Brunswick, Georgia, over 700 miles away.
22:40The sonar scans reveal that huge sections of the collapsed bridge are anchored deep in the mud on the riverbed.
22:48This will make the task to remove the wreckage even tougher.
22:56Engineers bring in 22 massive floating cranes, some urgently reassigned from other jobs, 130 miles away.
23:06These cranes can lift up to 500 tons.
23:11But even that isn't enough.
23:15Some of those pieces were more than a thousand tons.
23:18They must risk destabilizing the tangled mess by cutting the massive truss sections into more manageable pieces.
23:27So we kind of had to figure out how many bites do we have to take out of this large structure that's underwater.
23:36How do you eat an elephant one bite at a time?
23:39But each bent steel beam holds a potentially lethal surprise for the workers about to cut through them.
23:50They're loaded with enormous stored energy, just like compressed springs.
23:55As we started cutting and removing the first sections of steel, it was really challenging to figure out where the energy was stored in different members and how they would react.
24:10That stored energy of the bridge, I like to describe it like taking a metal slinky that has all that energy that wants to come like this but is held with the steel.
24:21When you cut that, all the energy is free and it'll break apart like that.
24:25And sometimes it's very dynamic and dramatic.
24:30We have people, crane operators, operating very close to this massive Jenga pickup sticks, loaded spring of a problem where members are being cut and then they spring back.
24:48It's very dangerous.
24:50Certainly make your hair stand up on the back of your neck, seeing the steel drop as you're making cuts.
25:03To speed up the job and lift out the biggest sections of bridge possible, the team calls in the largest floating crane on the East Coast.
25:11The Chesapeake 1000 is capable of lifting up to 1,000 tons.
25:18You're not just dealing with weight. You're dealing with all the forces that are working against you.
25:23There were days where we were battling specific sections due to mud suction.
25:28You have this force that wants to keep it sucked down in the mud and you're trying to apply a force that's coming opposite of that.
25:35So you have to break that suction force.
25:37And then as you're coming up out of the water, you have all this material just hanging off, dangerous roadbed, rebar and stuff.
25:46We had to get under there with small boats and torch cut and get that off of the structure.
25:51So from start to finish, it's just a very inherently dangerous world that we live in.
25:58The salvage team hopes to recover the bodies of the four missing construction workers as they remove the layers of steel and concrete.
26:18To get out onto the water, you go past the memorial, you see all the flags from their home countries,
26:23and the people that are gathered there, the families that were gathered there.
26:31When anyone was recovered, everything stopped.
26:35It was a very solemn and respectful moment.
26:40We were able to then return those people to their families.
26:53The complexity of the salvage leaves Baltimore's main shipping channel completely blocked more than three weeks after the collision.
27:15Hundreds of ships are unable to dock.
27:18To get shipping moving again, engineers open three temporary channels for smaller vessels.
27:29To restore around 15% of commercial shipping to the port.
27:33The next priority is to clear a 300 foot wide section of the deeper main shipping channel.
27:49That will allow single lane traffic for larger vessels and restore around 70% of shipping to the port.
27:56It takes almost four weeks to haul this wreckage from the mud.
28:09When we opened the limited access channel and you saw the scale of the ships that we were able to bring in.
28:16We just knew that we were getting one step closer to bring Baltimore back to full functionality.
28:22But this access channel creates another challenge for the team.
28:28Larger vessels disturb the water so much that the Dali could start to rock and roll.
28:37There's a risk the vessel could break free, swing around, and block the channel again.
28:44The team urgently needs to stabilize the ship.
28:47So they pump water into the ballast tanks at the front to weigh down the bow and lock it into the riverbed.
28:56To secure the stern, they drop four massive anchors.
29:02And they send in powerful tugboats to restrain the Dali should the ship break its chains.
29:08As the team races to secure the vessel, they must also devise a plan to remove the 5,000-ton truss resting precariously across the bow.
29:21The bridge section on the Dali was very unstable.
29:28There was bolts falling off it, pieces of steel falling off it.
29:32Taking care of the truss on the ship was going to be challenging and dangerous.
29:37The cost of the port shutdown exceeds $15 million a day.
29:49And this is not the first time in America that a ship colliding with a bridge has led to catastrophe.
29:55An incident more than 40 years earlier highlights the vulnerability of bridges, but also shows how to protect them from ship strikes.
30:09In 1980, a freighter called Summit Venture brought down a section of the Sunshine Skyway Bridge in Florida.
30:21And as I came to the very top of the bridge here, I saw the rest of the bridge was out and applied their brakes immediately and stopped with them and about two feet are going in.
30:30But 35 people lost their lives in this tragedy.
30:43The new bridge was built with engineered islands to protect the main piers from ship collisions.
30:50Vast underwater pillars, called dolphins, guard the piers that hold up the roadway.
30:56Dolphins, they're really anchored all the way down into the seabed and filled with concrete. So they're massive. They're not pushovers.
31:06They dissipate the energy and bring the ship to a stop.
31:11After 1991, all new bridges had to be built with pier protection.
31:17Bridges built before then were not required to be protected.
31:21They were kind of just left alone.
31:28So that's why a bridge like the Francis Scott Key Bridge was left unprotected.
31:36But retrofitting pier protection to older bridges is possible.
31:41Operators of the Delaware Memorial Bridge, which opened in 1951, decided to spend $93 million to install eight new dolphins.
31:54It would cost almost $2 billion to replace the Delaware Memorial Bridge in the event of a collapse, more than 20 times the cost of the dolphins.
32:03In the 1970s, the Key Bridge was built with four dolphins, but they were all positioned over 400 feet from its main piers.
32:18The dolphins were so far away from the piers that they were basically useless in terms of protecting the piers.
32:25I believe that if you had dolphins, a cluster of dolphins, protecting the Key Bridge, that direct heat from the dally would not have happened.
32:40The ship would be damaged, but the bridge would have been spared. The lives would have been spared.
32:46Maritime law is written in blood. We tend to wait for an accident to take place.
32:56It took Titanic sinking for us to come up with a convention that mandated enough lifeboats on board.
33:04It's because we can't imagine something as bad as what happens with Dolly ever happening.
33:09Since the Francis Scott Key Bridge opened in 1977, thousands of ships have passed safely underneath.
33:33But this disaster had been foreseen. Between 2006 and 2016, meeting notes reveal that Baltimore's Harbor Safety Committee discussed the need for the Key Bridge to be protected from ship strikes.
33:53There were people really stressing that there needs to be peer protection.
33:58You could have ships lose electrical power, and if they lose electrical power, they could drift and hit the piers.
34:07But the issue of cost is discussed, and it seems crazy, but nothing was done.
34:14There was a real opportunity to prevent what happened.
34:20The Dolly is not even the first ship to strike Baltimore's Key Bridge.
34:25On August 29, 1980, a 400-foot-long cargo ship also lost power leaving port and slammed into the same pier that the Dolly would hit over four decades later.
34:40Here's where it happened.
34:42Here's where it happened. A Japanese ship called the Blue Nagoya was heading south out of Baltimore Harbor when it rammed right into Key Bridge.
34:49As you can see, it tore off about 30 feet of planking and damaged part of the bridge's support structure.
34:55The Blue Nagoya was a large ship for 1980, but it was only about a third the size of the Dolly.
35:05Even so, the ship caused half a million dollars' worth of damage to the Key Bridge.
35:10The fender was badly damaged and had to be replaced. So that was a warning sign. It was something that they knew had happened before.
35:21So if it had happened before, the probability that it would happen again was always there.
35:26But the damage the Dolly would cause on March 26, 2024, was completely unprecedented.
35:39That morning, the ship was on the correct course to sail directly between the main piers of the bridge.
35:45So what caused it to veer to the right and head straight for the bridge pier?
35:58The ship's data recorder reveals that the Dolly lost power at 1.25 in the morning and started to drift rudderless at 9 knots.
36:07At that time, the vessel was sailing closer to one side of the shipping channel, possibly causing pressure differences along the ship's hull that may have pushed the bow to the right.
36:19At that precise moment, the ship passes the mouth of a river tributary, whose currents may have pushed the stern to the left, and set the ship on a collision course with the bridge pier.
36:30With no propulsion to correct its course, the 124,000-ton juggernaut was only seconds from disaster.
36:41If they lost power 30 seconds earlier, 30 seconds later, you probably don't have the collapse of the key bridge.
36:4930 seconds earlier, the ship may have sideswiped the pylon, it may have gone aground inside the bridge.
36:5530 seconds later, it may have coasted under the bridge and not hit it.
36:58It's now over six weeks since the Francis Scott Key Bridge collapsed.
37:13As teams prepare to move the stranded Dolly, they continue to hunt for the sixth and final missing construction worker.
37:22The recovery never stopped until every single person was found.
37:26Finally, with most of the mangled mass of steel out of the way, they must remove the truss pinning down the Dolly, so they can tow the vessel away and clear the shipping channel.
37:53This will be a huge challenge.
37:57There's so much pressure, compressive pressure, on the beam from how it's laying.
38:03That's very dangerous if you have someone in the way and all of a sudden it's going to give way.
38:08So, the best thing to do is to remove the human from the equation.
38:14Using controlled demolition was the fastest and safest way to conduct that many cuts all at the same time.
38:21Workers make cuts at strategic points, but do not fully sever the beams.
38:28Then they insert specially shaped charges, explosives that create high velocity jets to slice through the steel and complete the cuts.
38:37The charges must now explode, so the 5,000-ton truss section falls safely away from the ship.
38:49It's now seven weeks since the disaster.
38:53The Dolly's crew continues to assist with the investigation, and visa restrictions still prevent them from leaving the ship.
39:01With safety measures in place, they are moved to the stern, away from the blast.
39:07This is a critical operation engineers have been meticulously preparing for.
39:16But have they thought of everything? Are all their calculations correct?
39:25Blast day was set. The time was set.
39:30We had a blast radius that we had to stay outside of and, you know, a safety zone set up.
39:43We were telling people it wasn't going to be, as you see in the movies, a big explosion.
39:47But at the end of the day, it turned out to be a pretty big explosion.
40:00Feeling the boom and then seeing it fall in the water, it was pretty magnificent. It was pretty cool.
40:08I mean, I've never seen anything like it before.
40:22But then I was thinking, all right, what do we have to do to go get this, like, out of the water?
40:31Finally, after eight weeks of cutting and lifting wreckage from the river, they free the ship from the metal.
40:41They pump water out of the ship's ballast tanks to help raise the Dolly off the riverbed.
40:50And that's when she came free and floated up, and we were able to pull her off.
40:54A fleet of 5,000 horsepower tugs helps haul the ship away from the devastated pier.
41:24Finally, 11 weeks after the accident, the salvage team removes the last of the wreckage, fully restoring shipping to the port of Baltimore.
41:36Seeing the first deep draft ship come through that channel, I felt like there should have been fireworks behind it, you know?
41:43It was an accomplishment for everyone.
41:44This highly coordinated, complex salvage operation clears the way for the port of Baltimore to reopen.
41:59It costs over $100 million to clear the wreckage.
42:02And it could cost almost $2 billion more to replace the key bridge.
42:09A number of lawsuits against the Dolly's owners allege that poor maintenance and cost cutting caused the ship to lose power and hit the bridge.
42:19The ship's owners reject these allegations, but if upheld, maritime insurers estimate that the total claims could approach $4 billion.
42:33Ever since the crash, the National Transportation Safety Board's lead investigator, Marcel Meuse, has been working to find out what caused the Dolly to lose power.
42:43His team has now released preliminary reports that suggest how a series of unfortunate events may have led to this tragedy.
42:54Why the ship lost power is absolutely the focus of the investigation.
42:59We want to prevent this from happening again.
43:02Ships are complicated.
43:04They need electrical power to run a variety of systems, including propulsion and steering and navigation.
43:10The investigation reveals that on the night of the crash, the Dolly was running two of its four power generators.
43:19Together, they produce over eight megawatts of electricity to power nearly everything on the ship, including the fuel and water pumps for the main engine and the hydraulics of the steering mechanism.
43:33Ships generate a great deal of electricity to run.
43:38And much like your own house, where you have circuit breakers to ensure that if there is a disruption or a problem, they'll trip, ships have them too.
43:47The investigation discovers a loose cable, which lawsuits claim were shaken loose by engine vibrations, causing a power surge that tripped two breakers, disrupting the electrical power supply.
44:02The system should have automatically switched to a secondary circuit, but lawsuits alleged the control was set to manual, so did not automatically switch, causing a blackout across large parts of the ship.
44:19The pumps required to run the main engine and steering all shut down, which killed the propulsion and locked the rudder in place.
44:28When they are about three ship lengths away from the bridge, the ship lost power.
44:38Having sailed for many years on a ship, I can tell you that the worst sound you ever hear on a ship is silence.
44:48When everything goes quiet and dark, it is the worst feeling, because at that moment you realize you don't have control of the ship anymore.
44:56It is a nightmare, a nightmare scenario to be up on a ship when it loses power in close quarters.
45:06You have a very short period of time in which to try to restore power.
45:11From the time period that Dolly lost power until it hit the bridge was four minutes.
45:15A small emergency generator kicked in, and the crew closed the trip breakers.
45:23Lighting came back on, but the engine was still offline.
45:29When the ship goes dark, the main propulsion engine of the ship also cuts off.
45:33It is not getting the fuel, the lube oil, the water.
45:36You basically have stalled that engine.
45:39But before the crew had a chance to restart the engine, there was a second blackout.
45:46Investigators discover that the generators caused this outage.
45:51One lawsuit claims that after the first blackout, the pump supplying the generators with fuel shut down.
45:59And even when the power came back on, this pump did not restart automatically.
46:04The generators would then have lacked fuel pressure, which could have caused them to run erratically.
46:11Creating power fluctuations that tripped the breakers.
46:15And caused the ship to go dark again.
46:19They never were able to get the propulsion going again.
46:23After the second blackout, the ship was about 1.6 ship lengths away from the bridge.
46:29The timing of the blackout was exceedingly unlucky.
46:32But the blackout itself was far from unusual.
46:37Ship blackouts happen surprisingly frequently.
46:41On average, over five large vessels lose power every week in the U.S. alone.
46:48Fortunately, few of these result in collisions.
46:52Most of the time these blackouts occur at sea, when the ship is sailing out in the ocean.
46:57It takes a bit of time to find the underlying cause that is creating the fault.
47:05And as Dolly was approaching the Francis Scott Key Bridge, the one thing that crew did not have was time on their hands.
47:11The Dolly's log reveals that in a last ditch attempt, the crew tried to power up the bow thrusters and drop an anchor.
47:21But the thrusters were offline.
47:25And the break to lock off the anchor could not be applied.
47:29By the time the anchor was dropped, they were coming up on top of the bridge.
47:34The crew member on the bow had to evacuate before Dolly hit the bridge.
47:39The ship slowly drifted to starboard and they contacted Pier 17 of the bridge.
47:44The NTSB's preliminary report reveals the night of the accident was not the first time that the Dolly had experienced blackouts.
48:07The day before, while still in port, the ship lost power twice.
48:21This resulted in power being rerouted to a second circuit, which had not been used for months.
48:27This is the circuit with the loose cable that's alleged to have possibly caused the fateful blackout the following morning.
48:39This loss of electrical power triggered a cascade of disasters that affected the lives of countless people.
48:47None more so than the construction workers who were fixing potholes on the Key Bridge that night.
48:57I know the journey of healing for Baltimore is going to be a long road.
49:06I know that for those families who lost individuals, this is a burden they will feel for the rest of their lives.
49:15Six lives were lost in the collapse of the Francis Scott Key Bridge.
49:20But the accident could have been far worse.
49:22You have to remember this didn't happen during rush hour in Baltimore when that bridge has hundreds if not thousands of people going over it.
49:31When the Dolly first lost power, one of the ship's pilots put out a distress call.
49:38Maryland police were controlling traffic around a lane closed off for the road workers, so quickly began to shut down bridge traffic.
49:45Cars would have kept coming had they not stopped traffic, and by the time the people driving the vehicles would have realized the bridge was gone, it just would have been too late.
49:58I can't tell you how many lives they saved because the answer is countless.
50:02The last moving vehicle cleared the bridge just 40 seconds before the Dolly brought it crashing down.
50:11We got a call, I mean like probably a minute if that, before it hit it.
50:20Unfortunately, the police were unable to reach the construction workers to warn them of the danger.
50:27The Francis Scott Key Bridge only stood for 47 years, but saw profound changes to shipping.
50:42In 1977, very few people foresaw a ship the size of Dolly.
50:48What we've seen is kind of the exponential increase in the amount of goods we move by sea.
50:52Bridges and safety measures have to keep pace with the way we're changing ocean shipping.
50:59An estimated two and a half thousand US bridges remain at risk of ship strikes, including the 72-year-old Chesapeake Bay Bridge, just 20 miles south of Baltimore.
51:10We can't let our old bridges be sitting docks.
51:17We can't just leave them unprotected, structure our peer protection, having tugboats, leave the ships, but doing something.
51:27Not just sitting and waiting and hoping that nothing happens.
51:31The National Transportation Safety Board has been calling on the Coast Guard and the Federal Highway Administration to review the adequacy of bridge pier protection since 1988.
51:45Now, an urgent assessment of ship collision risk is underway across the nation.
51:54It's possible that recommendations will include vast investment to safeguard the country's bridges.
52:02And in the end, many hope the lessons learned from the tragic loss of the key bridge will not be forgotten.
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