- Authorities worry that rough weather may push the ship out to deeper water.
- Diesel fuel must be removed from the ship, a process that will take at least several weeks, before it will become buoyant.
- A series of chains and pulleys in a winching system called "parbuckling" may finally right the ship.
How do you turn over a 952-foot cruise ship that's capsized on a rocky shoreline?
Marine engineers around the world are speculating on the best way to refloat the Costa Concordia, an operation that will begin as soon as authorities account for all the missing passengers.The Italian ship with 4,200 passengers and crew ran aground Friday in 45 feet of water as it was passing the island of Giglio off the coast of Tuscany. As of Tuesday, 11 people had been killed and more than a dozen were still missing.
Although the ship lies on its starboard side and is in shallow water just offshore, Italian coast guard authorities fear that worsening weather is pushing it into deeper water which could make the rescue and salvage operation more difficult. Italian environmental officials have also asked the ship's owner, Miami-based Carnival Cruise Cruise Lines, to come up with a plan to remove 2,000 metric tons of diesel fuel that remain in the hull of the stricken liner.
"Nobody wants a wreck removal where you have to chop it up," said Joe Farrell III, a marine salver and naval architect at Resolve Marine Group in Fort Lauderdale, Fla. "You want to take enough weight off it so it will float off the bottom. The thing is on its side. You'd need to roll it right side up and you would need a crazy amount of force to do that."
Farrell recently returned from Sri Lanka where he salvaged a group of four ships, and also rescued a stranded cruise ship in the Arctic Canadian waters last year. Once the diesel fuel is removed from the ship, a process that will take at least several weeks, it will become more buoyant.
Salvers also may decide to force air into its ballast tanks in order to blow out water that has leaked through a 165 foot gash along the side. The damage would likely be repaired only after workers cut away the jagged edges around the gash and weld steel plates to the hull. The entire operation can be modeled on computer programs that predict the kinds of stresses that the ship can handle.
Once the hole is patched, Farrell said that airbags could be placed under the hull to help stabilize the ship. They may not be enough to right-size it. That would be done using a series of chains and pulleys in a winching system called "parbuckling."Special marine chains made with 90-pound, 18-inch links are wrapped around the ship and then pulled around a pivot point or "deadman" that is anchored either into the sea bed or onshore. A winch then slowly pulls the ship back over.
"You're talking 5,000 to 6,000 tons of force," Farrell said. "It's got to be one of the biggest operations ever."
Marine salvage operators from Seattle to Greece are already eyeing the prize of repairing and refloating the massive Costa Conordia, which contains four swimming pools, five restaurants, 13 bars and a casino.
Some experts say the trend of ever-bigger cruise ships pose a danger on the high seas. It's not just the size of the ship, but the number of people on board, according to James Herbert, a spokesman for the International Salvage Union, a London-based trade group representing salvage operators. "Evacuating those passengers and handling them safety far out to sea is a matter of considerable concern," he said.