The worst offshore oil spill in U.S. history was caused by a 1.4-inch hole. A new report reveals that the blades designed to seal Deepwater Horizon's well from leaking were jammed by the power of the April 20, 2010 blowout, leaving 1.4 inches of space through which 4.9 million barrels of oil eventually flowed.

The report, which was based on an investigation conducted by federal investigators and Norwegian engineers, "concluded the blowout preventer failed as a result of a design flaw, now because of misuse by BP or any of the other companies involved, and not because of poor maintenance," The Wall Street Journal's Ben Casselman and Russell Gold report. "Even if the device had worked, it wouldn't have saved the lives of the 11 rig workers killed in the accident. But the device could have mostly prevented the oil spill that began when the Deepwater Horizon sank two days after the initial explosion."

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Caitlin Dickson