Even at over 1m barrels and counting, the Deepwater Horizon disaster is not yet the biggest oil spill in history, or even in US history. But it is already shaping up to be the costliest.
The biggest-ever oil spill is thought to be the Lake View Gusher, an exploration well that accidentally punctured a massive oil reservoir in Kern County, California, back in 1909. The vast geyser blasted oil over the surrounding scrubland for well over a year until it collapsed in on itself. By that time, some 11m barrels had spewed out of it. Another horror was the spill that occurred during the first Gulf war, and which deposited a similar amount of oil into the Gulf of Persia.
Technically, the Deepwater Horizon disaster is similar to the Ixtoc spill in 1979. Then, as now, the failure of a blow-out preventer resulted in a massive gas explosion, destroying the rig and rupturing the well on the seabed. By the time it was contained, some 3m barrels had leaked into the Gulf of Mexico.
Until the latest catastrophe, the biggest US spill in recent times was the Exxon Valdez disaster in 1989. The supertanker struck a reef in Alaska's Prince William Sound, dumping 250,000 barrels of crude into a pristine natural wilderness. However, Exxon's share price suffered remarkably little compared with the pounding BP has taken, as the graph shows.
It's hard to quantify how much the disaster cost Exxon, because even 20 years later, the litigation is ongoing. Initially, $5bn of punitive damages were awarded, but that was cut to $2.5bn in 2006 and the company is still going through the appeals process. The cost of Deepwater Horizon to BP is likely to be very much higher - not only because of the politicisation of the disaster, but because the commercial and human impact is greater in the Gulf of Mexico than in largely unpopulated Alaska. In short, seagulls don't sue.
Amid all the criticism of BP's response, it's interesting to note that although the Ixtoc well-head lay just 150 feet beneath the surface (compared with 5,000 feet for the Macondo well that Deepwater Horizon was drilling), it took the Mexican state oil company 10 months to plug it. Even that performance was better than the UK's response to the 1967 Torrey Canyon disaster, when a tanker ran aground off the Scilly Islands. At that time, few governments anywhere in the world had any idea how to contain big oil spills, and the UK's strategy of bombing, burning and spraying the slick was widely derided afterwards.
