GIGLIO, Italy—The rotation of the crippled Costa Concordia cruise liner off the rocks of the Tuscan island of Giglio began at 9 A.M. today (September 16), three hours late due to a torrential overnight sea storm that halted preparations. The salvage crews had hoped to have the control room for the operation—a prefabricated container—in place on a barge less than 100 meters from the rusting hulk by first light. Instead, operators had to hustle to put the room into place when the rough seas calmed.

A salvage team of 500 people from 26 nations has been working around the clock for more than a year leading up to today’s rotation, called parbuckling (see graphic here). The 290-meter-long ship has been lying on its side at about a 45-degree angle, snagged on two large rock outcroppings along the island’s shore. Tall towers with pulleys called strand jacks are pulling the ship from the bottom towards Giglio Island with thick cables attached to the ship’s underbelly. At the same time, cables attached to large, empty buoyancy boxes called sponsons or caissons, which have been welded to the side of the vessel sticking up out of the water on the sea side, are also pulling the Concordia upright toward the ocean from the top of the ship. For the first two hours of the operation, there were no visible signs of the massive liner’s movements, but then a faint rust-colored line appeared along the sunken side that faces shore, indicating the vessel was indeed slowly rotating upward. By the seventh hour, the 114,000-tonne ship had rotated a full 8 degrees.

By early afternoon, local time, salvage experts were preparing for what they call “zero hour” when the ship reaches a 20-degree rise. At that point, gravity will take over, rotating the hulk beyond the ability of the cabling to stop it. It is then that the experts will see if their plan worked. The ship is supposed to come down softly on a bed of steel platforms 30 meters below the water line. If gravity pulls too hard, the boat could topple over toward sea and sink. The platforms could also crumble under the weight, sending the ship scraping down the sea floor. Or the ship could break apart under its own weight. Any of those scenarios would cause an environmental disaster. If the parbuckling succeeds, however, the salvage operation will enter its next phase: preparing the ship, in place, so it can float again, and then towing it to the Italian mainland sometime next summer.

At about seven hours into the parbuckling, Franco Girotto, a manager at salvage firm JVC Titan Micoperi, said the rotation was on schedule, even if the operation seemed like it was moving at a snail’s pace. “The massive size of this ship is what dictates the speed at which we are rotating it,” he told Scientific American. “It would be too dangerous to move it any faster than this.”

Once the giant hollow flotation caissons on the sea side start dipping into the water as the ship continues to rotate, which should happen around 10 P.M. local time, the rotation should speed up considerably. At that point the control team will have only air to use to control water levels inside the hollow boxes, which will ultimately provide the buoyancy to counteract gravity. That will be the real test of the project. “We have faith that our plan is going to work,” Nick Sloane, the project’s salvage master, said the day before the rotation began. “We have tested and allowed for every possibility and challenge.”

You can follow this author’s tweets about what is happening at @BLNadeau and world coverage at #Concordia.