The report was jointly authored by the Bureau of Ocean Energy Management, Regulation and Enforcement in the U.S. Interior Department and the U.S. Coast Guard.
An introduction to the report said the investigation "concludes that BP, Transocean and Halliburton's conduct in connection with the Deepwater Horizon disaster violated a number of federal offshore safety regulations under [the agency's] jurisdiction."
The report's executive summary said the joint investigative panel "found that a central cause of the blowout was failure of a cement barrier in the production casing string, a high‐strength steel pipe set in a well to ensure well integrity and to allow future production. The failure of the cement barrier allowed hydrocarbons to flow up the wellbore, through the riser and onto the rig, resulting in the blowout. The precise reasons for the failure of the production casing cement job are not known."
The panel determined that the "loss of life at the Macondo site on April 20, 2010 [11 rig workers were killed], and the subsequent pollution of the Gulf of Mexico through the summer of 2010 were the result of poor risk management, last‐minute changes to plans, failure to observe and respond to critical indicators, inadequate well control response and insufficient emergency bridge response training by companies and individuals responsible for drilling at the Macondo well and for the operation of the Deepwater Horizon."
The report said, "BP, as the designated operator under [the agency's] regulations, was ultimately responsible for conducting operations at Macondo in a way that ensured the safety and protection of personnel, equipment, natural resources and the environment. Transocean, the owner of the Deepwater Horizon, was responsible for conducting safe operations and for protecting personnel onboard.
"Halliburton, as a contractor to BP, was responsible for conducting the cement job, and, through its subsidiary (Sperry Sun), had certain responsibilities for monitoring the well."