5 key human errors, colossal mechanical failure led to fatal Gulf oil rig blowout
 

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A string of mistakes, first by people, then by a supposedly fail-safe machine, sealed the fates of 11 rig workers and led to the fouling of the Gulf of Mexico and hundreds of miles of its coastline.

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The Deepwater Horizon oil rig burns and collapses into the Gulf of Mexico on April 22, two days after the well blew, killing 11 workers on board the rig.
More than 100 hours of testimony before a federal investigative panel, two dozen congressional hearings and several internal company reports have brought the genesis of the spill into sharp focus. The record shows there was no single fatal mistake or cut corner. Rather, five key human errors and a colossal mechanical failure combined to form a recipe for unprecedented disaster.

The rig's malfunctioning blowout preventer ultimately failed, but it was needed only because of human errors. Those errors originated with a team of BP engineers in Houston who knew they had an especially tough well, one rig workers called "the well from hell." Despite the well's orneriness, the engineers repeatedly chose to take quicker, cheaper and ultimately more dangerous actions, compared with available options. Even when they acknowledged limited risks, they seemed to consider each danger in a vacuum, never thinking the combination of bad choices would add up to a total well blowout.
Tens of thousands of offshore wells have been drilled without incident. Drill teams often face difficult conditions miles down in a hole, but they use a battery of tests and equipment to proceed safely. That's why the first time BP went with the less-than-safest option -- choosing a well structure with fewer barriers against kicks of gas -- nobody batted an eye.

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