CSB Report Says Similar Accident Could Still Occur. The blowout preventer (BOP) that was intended to shut off the flow of high-pressure oil and gas from the Macondo well in the Gulf of Mexico during the disaster on the Deepwater Horizon drilling rig on April 20, 2010, failed to seal the well because drill pipe buckled for reasons the offshore drilling industry remains largely unaware of, according to a new two-volume draft investigation report released by the U.S. Chemical Safety Board (CSB).