GIGLIO ISLAND, Italy—On May 6 salvage workers at the Costa Concordia wreckage off the Tuscan island of Giglio heard the worst sound possible on any such operation—groaning, bending steel. It was a sound they hoped not to hear when the ship was rotated to an upright position last September in a procedure known as parbuckling.  And it is a sound they continued to listen for every day since, with microphones and monitors placed all over the ship. Around 5:30 P.M. on the recent, calm spring afternoon they unfortunately heard what they feared—loud and clear. “It was exceptionally loud for everyone in the area,” Nick Sloane, head of the Titan Micoperi joint venture tasked with the removal of the ship, told Scientific American. “It is the sound you don’t want to hear on a job like this.”

Sloane is heading up a massive, multiyear effort to remove and float away the heavily damaged cruise ship as well as all the diesel fuel, lubricants and other chemicals onboard from the site, home to pristine coral reefs, sea grasses and spawning grounds. In January 2012 Costa Concordia crashed on rocks off the island, 19 kilometers off Italy’s western coast, resulting in 32 deaths.

The noise occurred last week when a caisson, a hollow box 30 meters tall and filled with water and air, partially detached from the Concordia’s battered side just days after it had been attached to the sunken ship. During the next two months, a total of 15 caissons will be attached to the previously submerged starboard side of the ship (to match 15 already on the port side), including the one that detached last week—called S13. The caissons are part of an intricate buoyancy system that was used to rotate the ship upright, and which will be used to refloat it sometime this summer or early fall. The ship was heavily damaged in the two areas where it rested on underwater mountain peaks for 20 months. Those sections are not flat, so the salvage teams had to engineer metal skeletons on which to attach the flotation caissons in a horizontal position rather than a vertical position like the others. The rogue S13 was the first of the horizontal caissons to be attached to the ship.

Divers who were on the underwater portion of the wreck at the time the S13 caisson came loose told Scientific American that they felt a vibration and looked up to see movement. They got out of the way as fast as they could. Luckily no one was injured, but S13 detached completely from the ship a few hours later in what was described as “an even louder bending and scraping of steel” by workers who were on-site at the time. It had to be wrestled back to a horizontal position so it didn’t bounce around and damage other nearby caissons. According to Sloane, when S13 broke loose, it popped up something like a plastic bottle being held underwater.

The loose caisson is the first blip in an otherwise smooth salvage operation that has lasted more than two years so far and cost Costa Cruises, its American parent company Carnival and their insurers more than $1 billion.

According to the salvage team’s official statement, “technicians worked all night to bring back S13, [which had been] installed on the starboard side, in horizontal position.” Once this was accomplished, they loaded it onto a barge and sent it to Genoa to be repaired. Sloane says that at no time was the ship’s equilibrium compromised; the rest of the caissons will be installed while the S13 is being repaired. The Concordia is resting safely on massive underwater platforms on the seabed and kept upright by a series of chains, pulleys and caissons on the ship’s port side.

Once all 15 vertical and horizontal reflotation caissons are in place, likely around late June, salvage crews will be ready to refloat the ship in a process Sloane says could take several days, because the ship and environment must be monitored as water from inside the vessel pours into the sea. Because Costa Cruises has not yet determined the destination port, Titan Micoperi Joint Venture may be delayed until September simply because they have nowhere to take the ship once it is afloat.

Twelve different ports from six different countries as far away from Italy as China and England have bid for the lucrative final dismantling project, but the short list has been narrowed down to ports in Turkey and Italy. Two possible towing scenarios for the Concordia are at play, depending on its final destination. If the wreck will be broken down in a nearby Italian port, likely Civitavecchia or Genoa, Titan Micoperi can slowly tow it there. If Costa awards the salvage project to a port in Turkey, which will save them more than $60 million, it will be floated onto the Dutch owned Dockwise Vanguard, the world’s largest submersible heavy transport ship, which can act as a floating dry dock. Costa has confirmed provisionally renting the Vanguard for $30 million in case they need it. Costa Cruises told Scientific American the port would be announced by the end of May.

After the Concordia is gone, Titan Micoperi will keep a small cleanup team in place on Giglio for as long as it takes to remove all the implements of the massive salvage operation. The island of Giglio is expected to hold a referendum at that point to vote on whether to keep the massive underwater platforms in place to create what would be the largest dive site in the Mediterranean or to remove them, leaving no trace of the accident that marred their shores.