The salvage firms charged with removing the wreck of the Costa Concordia have set out in detail how they will refloat the ship.
The operation has been described as “the most ambitious effort of its kind” ever attempted and will cost over $300m.
“This is the largest refloat in history,” said Richard Habib, president of Titan Salvage, which has teamed with Italian company Micoperi to mount the operation.
“The magnitude of the job is unprecedented. But we feel confident that we can do it and do it safely, with the least disturbance to the environment and the economy of Giglio."
Work is due to start in the next few days and is expected to take a year, with the wreck set to be towed to an Italian port in one piece and then scrapped.
The port has not yet been chosen but the most likely candidates are Genoa or Savona on the Ligurian coast or Livorno in Tuscany.
“The technique is standard but the next largest vessel with which we have attempted this type of salvage was a 35,000t ship in Alaska,” said Guidotti Alvaro, an assistant project manager with the salvage team.
Salvors will initially build a 40 metre square undersea platform on the seaward side of the ship, before welding empty steel compartments or ‘caissons’ to the ship’s port side.
They then plan to use two cranes fixed to the platform to roll the vessel into an upright position on the platform.
As the caissons tilt into the water, water will be pumped into them to help the ship’s movement, while cables attached to the land will ensure the ship does not slide off the platform.
Once upright, the team will attach another panel of caissons to the starboard side. All the caissons will then be emptied of water and filled with air, prompting the ship to float.
The ship is punctured by the collision as well as by holes blown by divers searching for bodies. But the team will not attempt to patch those holes or drain the ship.
“We don’t need to seal the ship since the boxes give it sufficient buoyancy,” said Alvaro. “It’s just like a cargo ship except the cargo is water,” he added.
The team will however remove the large chunk of torn-off rock which became embedded in the hull at the moment of the collision.
Habib conceded to reporters that the operation entailed significant risks and said that if it went wrong there was no “plan B”.
“There are two critical stages – to roll the vessel onto the platform and then to safely refloat it. We think our plan is going to work and that we will be successful.”
“We are now launching a salvage operation with characteristics and technical complexities that have never been faced before,” said Costa Cruises president Gianni Onorato.
The Concordia has been wedged on rocks and half submerged off the Tusan island of Giglio since it ran aground in January.
Thirty bodies have been recovered but the remains of two people – an Indian and an Italian - are still missing and may be inside the wreck.
