Costa Concordia disaster
The super-sized cruise ship Costa Concordia is half-submerged off Italy's Tuscan coast. So what will happen to the 450-million-euro (£372m) vessel?
As divers desperately scour the 1,500 cabins for signs of life, and hopes fade of finding more people alive, thoughts have turned to rescuing the ship.
Maritime salvage specialists already have staff at the scene assessing the Can a stricken cruise ship be salvaged?options.
"Only a few salvage companies could handle a job of this magnitude," says Mike Lacey, secretary general of the International Salvage Union.
"This goes on all the time but you don't hear about it because they aren't as spectacular as this one. But there's always a ship in trouble somewhere."
So what might be the fate of the Costa Concordia in the weeks, months and possibly years ahead?
1. Underwater inspections
Search and rescue has priority, that's always the case, says Mr Lacey, but other underwater inspections will be under way to see what damage the rocks have wreaked to the hull.
"You can see the terrific damage above the waterline but who knows what has happened to the [submerged] starboard side of the hull?
"You can't put a ship like that on the rocks without doing damage."
2. Pumping out the fuel
Costa sinking: How it happened
Although there is no evidence that any of the ship's 2,000 tonnes of diesel oil has yet leaked, there are fears that if it slips on the rocks, one of the 17 tanks could breach and cause a spill.
The island's mayor has warned of an "ecological time-bomb", and anti-spill booms encircle the ship to minimise the threat of an environmental disaster.
A Dutch company specialising in salvage operations, Smit, has been asked to remove the fuel.
Its operations manager Kees van Essen said the company was confident the fuel could be safely extracted through a system of pumps and valves which vacuum the oil out to waiting tanks.
The process, involving engineers and divers, would take two to four weeks.
3. Getting it upright
End Quote Dawn Gorman International Tug & OSV
It may be the ship isn't salvageable and it isn't possible to right it, patch it up and send it on its way”
A statement by the parent company, Costa Crociere, said the ship could be lifted with "balls of air" and once floating, towed away by tugs.
The process is called parbuckling, an old-fashioned way to get ships upright, says Mr Lacey. This involves barges with huge winches slowly heaving the ship into position, bit by bit.
"You need a huge turning movement - the power you need to apply to pull the thing into the vertical position. It's simple physics.
"There was a similar operation on the [capsized ferry] Herald of Free Enterprise in 1987 but that ship was a quarter of the size."
Air bags could be placed under the starboard side by divers and then inflated to help push it upright, he adds, but those alone would not have sufficient force.
4. Removing what's inside
There is a huge amount of food on the ship, which will smell if not removed.
And the passengers' belongings in cabins on the port side will also need to be recovered, says Mr Lacey.
Much of what is inside the ship and below the sea level is likely to be written off, he says.
Some of it is has already floated to the surface.
"A lot could be replaced quite easily but the bigger damage is to the bottom of the ship - the machinery and electronic systems."
5. Patching up the hull
"It's possible, with small areas of damage, to prefabricate a [steel] patch and put it into place," says Dawn Gorman, editor of the magazine, International Tug & OSV.
"But whether that's possible with damage this size, we don't know."
If it could be patched up, the next step would be to pump the water out and stabilise it, a very lengthy process, says Ms Gorman.
"But there's no point pumping the water out unless the damage has been patched up, and that's a big hole.
What happened to other ships?
- 1987: Car ferry Herald of Free Enterprise was parbuckled upright and towed away but scrapped
- 2002: Car ferry Tricolor cut up after collision
- 2007: Container ship MSC Napoli broken up after difficulty in the English Channel
- 2012: Container ship Rena broke up itself after three months aground near New Zealand
"It may be the ship isn't salvageable and it isn't possible to right it, patch it up and send it on its way, because fundamental damage has been done."
Last month the container ship Rena broke in two near New Zealand, after constant battering by the ocean, three months after it ran aground.
That's unlikely to happen to the Costa Concordia, says Mr Lacey.
"Rena was in a very exposed position so she got smashed up, but you won't get metal fatigue in this case. There isn't a huge fetch [the length of sea over which a wind blows] so she won't start rusting any time soon."
6. Getting it towed
Once upright, towing the ship using tugboats is very straightforward, and means it could be taken away for full repairs.
The Costa Concordia might be large for cruise ships, but not compared to some oil tankers and bulk carriers.
But given the damage, it may just be cut up and taken away in parts for scrap. The insurer has to assess the cost of repairs and the cost of getting it into a position to repair it.
What's the deal with insurance?
- A normal salvage operation to recover a ship is paid for by the ship's insurers
- But if a ship becomes a write-off and has very residual value under scrap, then the wreck removal operation is paid for by those underwriting the liabilities of the ship owner
Source: International Salvage Union
"There's every possibility that it could be salvaged but it's going to be a very tricky salvage operation," says Richard Meade of Lloyd's List, a leading daily newspaper for the maritime industry.
"I think the likelihood is that this is going to be declared a total loss."
The car carrier Tricolor was cut up into nine sections after it sank in 2002 in the English Channel following a collision with a container ship.