Repsol-YPF, the private Spanish oil company, said this week it expects to remove 90 percent of the oil remaining in the wreck. The rest is stuck on the tanker walls and eventually will be eaten away by bacteria.
The Prestige split apart in a storm off the Galicia coast and sank on Nov. 19, 2002, disgorging most of its 77,000 tons (20 million gallons) of thick, toxic fuel oil onto the beaches of northern Spain and southwestern France. It was Spain’s worst environmental disaster and was the eighth largest spill on record.
About 20,000 tons (5.3 million gallons) of oil sank four kilometers (2.5 miles) to the bottom of the Atlantic Ocean at a distance of 270 kilometers (167 miles) from Galicia.
Using an innovative technology it devised, Repsol removed 5,600 tons (1.5 million gallons) by perforating the tanker, allowing the lighter-than-water oil to rise, and capturing it in plastic bags.
About 13,800 tons (3.7 million gallons) remains in the wreck. During a tour of Repsol’s technology and research center in Mostoles, south of Madrid, company officials on Monday explained the technique.
Through holes drilled in the vessel, the oil floats out ? because it is less dense than sea water ? into double-lined plastic bags that are 30 meters (98 feet) tall, equivalent to the height of an eight-story building. The bags are then shuttled to just under the ocean surface for transfer to a boat.
The process takes about four hours for each bag. The oil is then taken to a refinery by land.
Oil has never before been removed from this depth.
The cost of the project is about euro99 million (US$122 million), the government recently said.