Never before have engineers tried to right such a huge ship so close to land. If the operation succeeds, the Concordia will be towed away and broken up for scrap.
Salvage experts had originally hoped to right the 115,000-ton vessel last spring, but heavy storms hampered work. Crews have raced to get the Concordia upright before another winter season batters the ship against its rocky perch damage that would increase the chance that it couldn't be towed away in one piece.
Salvage master Nick Sloane seemed optimistic in the final hours before the operation began, saying Sunday that testing of the machinery in recent days had actually lifted the 985-foot ship up about 2.5 inches. There have been concerns that the rocks of the reef on which the Concordia is resting were so embedded in the hull that the ship would resist being pulled off.
"We know that ... she is lively enough to move," Sloane told reporters.
The operation to bring the ship vertical involves dozens of cranklike pulleys slowly rotating the ship upright at a rate of about 3 yards per hour, using chains that have been looped around its hull. Tanks filled with water on the exposed side of the vessel will also help rotate it upward, using gravity to pull the exposed side down.
Once upright, those tanks and an equal number that will be fixed on the opposite side eventually will be filled with air, rather than water, to help float the ship up off the reef so it can be towed away.
Last week, the head of Italy's Civil Protection agency, Franco Gabrielli, said there was no "Plan B" if the rotation failed since there would be no other way to try again. But Sloane said he was confident the ship would withstand the stress of the rotation.
The most critical time will be the first hour or so of the operation, since that's when the ship will be detached from the reef.
This weekend, tourists and locals waded and swam in pristine waters just beyond the harbor, with the hulking wreck an ugly backdrop and reminder of the harrowing night when a few thousand people straggled ashore. Since the Concordia came to rest on its side, visitors have come to gawk at the wreck, providing the tiny fishing island a year-round tourist season it never had before.
Since the shipwreck, no major pollution has been found in the waters near the ship. But should the Concordia break apart during the rotation, absorbent barriers have been set in place to catch any leaks. Fuel was siphoned out early in the salvage operation, but food and human waste are still trapped inside the partially submerged vessel and might leak out.