The refloating of Italy's ill-fated Costa Concordia cruise ship is set to begin Monday, with a high-risk salvage operation to raise the rusting hulk ahead of its final journey to the shipyard where it was built.
Over two and a half years after it crashed off the island of Giglio in a nighttime disaster which left 32 people dead, the plan is to raise and tow away the 114,500-tonne vessel in an unprecedented and delicate operation.
"The most critical phase will be the first day, raising the wreck for the first time. Refloating a passenger ship this large has never been attempted before," South African Nick Sloane, who is in charge of the salvage, told AFP.
The ship was rotated upright off its side in September and is currently sitting on a vast underwater platform.
Thirty tanks or "sponsons" that have been welded to the sides will work as a gigantic pneumatic system to raise it.
Under the eyes of the world's media, the operation is expected to start on Monday with workers pumping compressed air into the sponsons to lift the Concordia by two metres.
"We are talking about a floating city kitted out for thousands of passengers, with gallons of pollutants such as oils, detergents and sewage chemicals still inside," said Giorgia Monti from Greenpeace, which is sending an observational team to monitor the operation.
Tug boats would then drag the wreck 30 metres east and secure it in place with anchors before it is slowly buoyed another 10 metres, with engineers checking each deck for fresh structural damage as they emerge from the sea.
The whole procedure is expected to take around six days.
Salvage costs so far are estimated at around 1.1 billion euros (USD 1.5 billion), including 100 million euros for the scrapping.
The luxury liner -- twice the size of the Titanic -- crashed into rocks just off tiny Giglio island in January 2012 and keeled over with 4,229 people from 70 countries on board.
The ship's captain Francesco Schettino is currently on trial for manslaughter, causing a shipwreck and abandoning the vessel before all of the passengers had been evacuated.
The body of one of the victims, Indian waiter Russel Rebello, is still missing and his remains may be found during the refloating or dismantling of the vessel.
The four-day journey to Genoa is fraught with possible environmental hazards.
The ship is also expected to leak some of the 263,000 cubic metres of polluted water flooding its lower decks, while fears remain for the estimated 100 tonnes of fuel which it was not possible to syphon out when the tanks were emptied after the crash.
