- "We're talking about big weights. We're talking about tons of force," says an expert
- Salvage costs could run into hundreds of thousands of dollars a day
- Re-floating the ship would be the "cleanest" approach, the expert says
- But that might not be possible, and the ship might be cut into pieces
U.S.-based salvage experts say no matter which method the owners of the wrecked Costa Concordia choose, the job of removing the ship will not be easy, or quick.
Whichever tactic the ship's owners choose, they will likely start with an assessment, according to salvage experts, and an effort to stabilize the ship.
"It's not so easy as simply chaining it down," said Bob Umbdenstock of Resolve Marine in Port Everglades, Florida. "This is a large object. We're talking about big weights. We're talking about tons of force."
Workers might also start with pumping out the fuel, to prevent it from leaking out and fouling the water and the coast. The ship, part of the Costa Cruises fleet, was carrying 2,300 tons of heavy fuel and gas oil, although there have been no indications of leaks or spills so far.
If the ship's own fuel pumps are no longer working, divers could use "hot taps" to drill holes from outside the hull, penetrating into the fuel tanks and pumping them out directly.
Next would be an assessment of whether there's a way to "de-water" the ship.
"The ideal option would be to simply pump it out and float (the ship) away," said Umbdenstock. "You'd like to think of that as being the cleanest approach."
To use that strategy, workers would have to restore the ship's buoyancy -- possibly by patching the hull, and then pumping out the water, or blowing it out with compressed air.
But according to Umbdenstock, that method depends on not only securing enough intact tanks, but also on correctly distributing the flotation throughout the hull, so that the ship is stable when it is raised.
One technique that could be used is called parbuckling -- righting a ship that is on its side by using ropes and stanchions to gain leverage, and then pulling the ship upright.
But re-floating and salvaging the ship may or may not be possible in this case, Umbdenstock said, and the owners may be forced to consider other wreck-removal options, in which only the scrap metal, or perhaps the engine room, can be saved.
"The other end of the spectrum," he said, "is to have to cut it up into pieces that you can lift out one by one and take them away."
That could involve chain-cutting, a technique where a cable coated with diamonds is used to slice it into pieces.
"Chain-cutting is where you actually wrap a large chain around the hull and you put all that tension on it, and the chain literally tears the metal apart," said Joseph Farrell III of Resolve. The resulting pieces could be towed away if they can float, or smaller pieces could be lifted with cranes.
Whichever method the owners choose, removing the remains of the ship will be no easy task.
According to the salvage experts at Resolve, the job could require an army of personnel, ranging from divers to engineers, it might take weeks or months to accomplish and the costs could run into the hundreds of thousands of dollars a day.