The Deepwater Horizon oil platform

Located approximately 80 kilometres off the coast of Louisiana, the Deepwater Horizon was extracting 8,000 barrels per day at the time of the accident. It exploded on 20 April 2010 and sank on 22 April 2010. A drilling pipe connected to the structure is believed to be the cause of the oil spilling into the ocean. After a fire, with rescue operations hampered by waves two and a half metres high, it sank, continuing to cause the discharge of one thousand barrels of oil per day into the ocean. The automatic shut-off system, which should have stopped the flow in the event of an accident, failed to function.

The black slick of oil

Reconnaissance flights by the US Coast Guard detected, the very day after the accident, a slick of 30 square kilometres approximately 60 kilometres from the coast. But the black tide continues to spread and is threatening the Louisiana coastline. Oil company BP, responsible for the Deepwater Horizon platform, has dispatched 32 vessels to the area to resume monitoring and clean-up operations that had been suspended due to adverse weather conditions. According to BP, the leak is coming from two holes five thousand metres deep on the riser that connects the wellhead to the platform that sank on Thursday. The Coast Guard has described it as "a very serious spill."

Containment measures

Alongside the 32 vessels sent by BP, an underwater robot is also in operation on site, active between 24 and 36 hours. The operation is, however, extremely complex and, despite the mobilisation, the outcome remains uncertain. It appears that BP is also preparing onshore response teams. A device fitted over the wellhead to contain the leaks has proved ineffective. "It has never been done before but we have the best-prepared experts working on it," operations chief Doug Suttles declared at a press conference. "What the company is trying to do – mechanical engineer Richard Metcalf summarised – is put a cork in a bottle of champagne." It will take two to three months to stop the leak.

Personnel on the Deepwater Horizon platform

At the time of the accident, 126 people were on board the Deepwater Horizon; 17 were injured. The search for the 11 people missing after the explosion, which was followed by a massive fire, was definitively called off on 26 April with no survivors found, CNN reports.

Damage to nature

In these conditions, oil emulsifies with the water, making recovery operations extremely difficult. Furthermore, at this time of year, the bluefin tuna spawning season is under way in the Gulf of Mexico, and the breeding season of four species of sea turtles is just beginning. Six species of whales are present in the area, and the coastal strip is home to over two million hectares of wetlands.

Back in 1979, an oil exploration platform belonging to the Mexican company Ixtoc I had already exploded in the Gulf of Mexico, causing the worst oil spill at sea (half a million tonnes of oil), and it took over nine months to seal the blown well. Mexico refused to pay compensation to the United States. Thousands of Kemp's ridley hatchlings (an endangered species) born on Rancho Nuevo beach had to be evacuated to save them.

Only in a few months' time, once the pipeline is closed, will it be known how much oil will have been spilled into the Gulf of Mexico: it could be a disaster even greater than that of the Haven.

The ranking of hydrocarbon spills at sea

After the Ixtoc I platform accident between 1979 and 1980 in Mexico, the worst in history, the most notable incidents are the Nowruz spill in the Persian Gulf in 1983 and the Abt Summer in Angola (1991). Among tankers, the worst disaster was the 200,000 tonnes of crude lost in 1978 off Brittany by the Amoco Cadiz, which shocked the world and set in motion international environmental legislation to prevent oil spills. Among many others, the following disasters also stand out:

• The Cyprus-flagged tanker Haven, which sank in 1991 off Genoa, still holds the record for spills in the Mediterranean.
• The Exxon Valdez in 1998 in Alaska, one of the worst disasters of all time and fully three times greater than that of the Erika.
• The Erika in 1999 spilled approximately 20,000 tonnes of crude off the Breton coast.
• The Jessica in 2001 spilled 200,000 tonnes of crude. It caused an outcry because it came close to the Galápagos Islands, a unique ecosystem, a repository of biodiversity and the cradle of Darwin's research.
• The Prestige in 2002, off the coast of Galicia, with the worst type of pollutant to deal with — dense, heavy, persistent and sticky, which cannot be dispersed even by rough seas.

Italy is among the seas at greatest risk

In the ranking of the most dangerous zones for oil traffic, Italy holds a far from enviable record: it accounts for the highest volume of traffic within the Mediterranean, which in turn leads the global ranking. In a body of water that amounts to less than one per cent of the total, 28% of the world's oil traffic is concentrated (350 million tonnes of crude per year, approximately one quarter of all oil exported globally): 300 tankers that together leave a black trail of 2,800 tonnes of oil per day, equivalent to 15 Prestige disasters per year (the tanker that sank off Galicia in 2002).