On April 20, 2010, the Deepwater Horizon rig was drilling BP’s Macondo Prospect 41 miles off Louisiana, in over 5,000 feet of water, with the well reaching another 18,000 feet into the crust. High-pressure methane breached the well, expanded up the riser and exploded on deck, killing 11 workers whose bodies were never recovered and injuring 17. The five-story blowout preventer failed: its hydraulics leaked, a critical battery was dead, and the buckled drill pipe kept the shear rams from closing. The rig sank on April 22, tearing away the riser and leaving an open wellhead a mile down.

BP first put the flow at 1,000 to 5,000 barrels a day, but the Flow Rate Technical Group found about 62,000, and internal emails showed BP’s own worst-case models matched the higher figure. A 125-ton containment dome clogged with methane hydrates, a top kill of drilling mud failed, a capping stack held in July, and a relief well sealed the well in mid-September after 87 days and an estimated 4.9 million barrels. Investigators cited BP for gross negligence and willful misconduct and also faulted Halliburton’s cement job and Transocean’s maintenance. BP paid over $65 billion and pleaded guilty to 11 counts of felony manslaughter, two environmental misdemeanors and lying to Congress, yet no executive served prison time.

• BP sprayed about 1.84 million gallons of the dispersant Corexit, which broke oil into droplets that formed deep underwater plumes.
• Up to a third of the oil mixed with silt and settled on the seafloor.
• Infant dolphins later died at six times the normal rate, and exposed tuna and amberjack developed heart deformities.
• Coastal families reported children with severe nosebleeds and bleeding from the ears.
• A BP engineer deleted text messages showing he knew the flow rate far exceeded public estimates.