A fireball visible from forty miles away
The Deepwater Horizon was an ultra-deepwater semi-submersible drilling rig, built in South Korea and completed in 2001, owned by Transocean and operating under lease to BP at the Macondo Prospect in the Gulf of Mexico’s Mississippi Canyon. On 20 April 2010, at approximately 7:45 in the evening, high-pressure methane gas from the well expanded up through the marine riser and into the rig itself, where it ignited and exploded, killing eleven workers and producing a fireball reportedly visible from forty miles away. A subsequent government investigation identified defective cementing of the well as a major cause of the blowout. The rig burned for two days before sinking on 22 April, leaving the damaged well gushing oil directly from the seafloor.
Eighty-seven days, 4.9 million barrels
What followed was the largest marine oil spill in recorded history. Oil continued flowing from the ruptured wellhead for eighty-seven days, from the initial explosion until the well was finally capped on 15 July 2010, with the well formally declared effectively dead on 19 September. Total volume released is estimated at approximately 4.9 million barrels, equivalent to around 210 million US gallons, with an uncertainty margin of about ten percent either way; the federal government’s own estimate placed roughly 4.1 million barrels as having actually entered Gulf waters, with the remainder captured or otherwise contained during the extended effort to bring the well under control.
A flow rate understated by a factor of ten or more
BP’s early public estimates of the spill’s severity proved substantially inaccurate. The company initially estimated the flow rate at somewhere between one thousand and five thousand barrels a day, a figure that shaped early public and regulatory expectations about the disaster’s scale. Later, more rigorous assessment put the actual flow rate at approximately 62,000 barrels a day, an order-of-magnitude discrepancy that meant the true scale of the ongoing spill was, for a meaningful stretch of the response effort, substantially understated in public communications, whether through genuine measurement difficulty at that depth or through more deliberate downplaying of the crisis’s severity in its earliest and most consequential days.
Birds, turtles, and a collapsing dolphin population
Environmental damage from the spill proved extensive and well documented. Estimates put bird deaths at between 51,000 and 84,000, and losses among juvenile sea turtles between 56,000 and 166,000, alongside an estimated two to five trillion newly hatched fish killed across the affected waters. The bottlenose dolphin population in Barataria Bay, a heavily oiled area of the Louisiana coast, declined by as much as fifty-one percent, and by 2013 more than 650 dolphins had stranded in the wider region, a fourfold increase over historical averages. Deep-sea coral and red crab communities across an estimated 400 to 700 square miles of seafloor also showed measurable damage from oil exposure that had settled well below the surface.
Manslaughter charges and a finding of gross negligence
BP’s attempts to contain the spill met repeated failure before eventual success. An initial effort to trigger the well’s blowout preventer failed, as did a 125-tonne containment dome deployed over the leak, defeated by the formation of methane hydrate crystals that blocked its structure, and a subsequent top kill procedure using heavy drilling fluid also failed to stop the flow. Relief wells, intended to intercept and permanently seal the original well from below, began drilling in early May 2010, and the leak was ultimately capped in mid-July, bringing to an end nearly three months during which the company’s containment efforts had visibly and repeatedly failed under close public and media scrutiny of the ongoing disaster.
The largest environmental settlement in US history
Legal consequences for BP proved substantial and prolonged. In November 2012, the company pleaded guilty to eleven counts of manslaughter, two misdemeanours, and a felony charge of lying to Congress, agreeing to 4.525 billion dollars in fines alongside four years of government safety monitoring. A federal district court ruling in September 2014 found BP primarily responsible for the disaster due to gross negligence and reckless conduct, a legal finding that exposed the company to substantially higher penalties than ordinary negligence would have allowed. The final major settlement, reached in April 2016, required BP to pay 20.8 billion dollars, the largest environmental damage settlement in American history, pushing the company’s total disaster-related costs past 65 billion dollars by 2018.