A complex system of pulleys and counterweights has begun an operation to pull upright the Costa Concordia cruise ship from its side on a Tuscan reef where it capsized in 2012, an anxiously awaited operation of a kind that has never been attempted on such a huge liner.
Engineer Sergio Girotto said the operation began at about 9am local time, three hours later than planned.
The delay was due to an early morning storm that pushed back a floating command room centre from its position close to the wreckage. There, engineers using remote controls were guiding a synchronised leverage system of pulleys, counterweights and huge chains looped under the Concordia's carcass to delicately nudge the ship free from its rocky seabed perch just outside Giglio Island's harbour.
The goal is to raise it from its side by 65 degrees to vertical, as a ship would normally be, for eventual towing. The operation, known in nautical parlance as parbuckling, is a proven method to raise capsized vessels. The USS Oklahoma was parbuckled by the US military in 1943 after the Japanese attack on Pearl Harbour. But the 1,000ft Concordia has been described as the largest cruise ship ever to capsize and subsequently require the complex rotation.
The Concordia crashed into a reef on January 13, 2012. Thirty-two people were killed after the captain steered the luxury liner too close to the rocky coastline of Giglio, part of a chain of islands in pristine waters.
The reef sliced a 230ft gash into what is now the exposed side of the hull, letting seawater rush in. The resulting tilt was so drastic that many lifeboats could not be launched. Dozens of the 4,200 passengers and crew were plucked to safety by helicopters or jumped into the sea and swam to shore. Bodies of many of the dead were retrieved inside the ship, although two bodies were never found and might lie beneath the hulk.
The Concordia's captain is on trial on the mainland for alleged manslaughter, causing a shipwreck and abandoning the ship during the chaotic and delayed evacuation. Captain Francesco Schettino claims the reef was not on the nautical charts for the liner's week-long Mediterranean cruise.
Asked how long it would take for people on shore to see the ship making significant movement towards the vertical, Mr Girotto said that "after a couple of hours, you should be able to see something visible from a distance". The first few hours will be critical, engineers predicted. Pieces of the granite seabed are embedded in the submerged side of the hull, which divers have not been able to fully inspect. The entire operation should take between 10 and 12 hours.
Parbuckling was supposed to begin before dawn, but daylight broke even before the barge carrying the engineers close to the ship could leave shore. After the storm blew away, seas were calm. Engineers have dismissed as a "remote" possibility the chance that the Concordia might break apart during rotation and no longer be sound enough to be towed to the mainland to be turned into scrap.
Costa Crociere, the Italian unit of Miami-based Carnival, is picking up the tab for the parbuckling and its intricate preparation. The company puts the costs so far at 600 million euro (£500 million), though much of that will be passed on to its insurers.