BARCELONA--The Spanish government is going forward with a pioneering attempt to salvage oil remaining from the wreck of the Prestige. The $100 million operation in deep waters off the Galician coast, set to begin in the spring, will deploy an ingeniously simple technique: It will decant the oil from the tanker's holds into giant bags and haul them to the water's surface.
During a heavy storm on 19 November 2002, the Prestige split in two and sank roughly 200 kilometers off Galicia near northwest Spain. At least 79,000 metric tons of oil ended up coating shellfish beds and polluting 900 kilometers of French and Spanish coast, inflicting about $1 billion worth of damage (Science, 29 November 2002, p. 1695). Last February, a scientific panel advised the government to extract or entomb the oil left in the wreck. The government opted for removal and tapped the Madrid-based oil giant Repsol to undertake the unprecedented operation.
Repsol had to come to grips with a "major technological challenge," says the company's technical director, Ramón Hernán. The Prestige lies almost 4000 meters below the surface, and no oil had ever been salvaged from so deep. With help from researchers at the University of Huelva and several foreign firms, Repsol adapted four remotely operated submersibles for the job. In field trials last month, the subs sealed some of the wreck's gaping holes, decreasing the amount of escaping oil from 700 liters to just 10 liters each day. The team also estimated that 13,700 tons of oil were left in the wreck, much less than previously thought.
To get that oil out, Repsol engineers turned to giant plastic bags. On 16 October, the team used a submersible to hook a 250-ton bag to the Prestige's bow before drilling a hole into one of the smaller holds. Over 18 hours, 100 tons of fuel flowed upward into the bag "without spillage into the sea," says Hernán. The bag was sealed and hauled to the surface by submersible. The technology "sounds promising," says marine biologist Richard Steiner of the University of Alaska, Fairbanks, who helped assess how the Exxon Valdez oil spill in 1989 harmed wildlife in Alaska's Prince William Sound.
Environmental Protection Agency oil spill site