The joint investigation by the U.S. Coast Guard and the Bureau of Ocean Energy Management, Regulation and Enforcement (BOEMRE) found BP -- as owner of the well -- "ultimately responsible" for ensuring the "safety and protection of personnel, equipment, natural resources, and the environment."
"BP's cost- or time-saving decisions without considering contingencies and mitigation" led to the series of events that caused the disaster in April 2010, the 200-plus-page report found.
But the investigators also placed considerable blame on BP's key contractors, Halliburton and Transocean. Hallburton was responsible for the cement work at the bottom of the well, meant to stop oil and gas from escaping; Transocean, the owner and operator of the drilling rig, was responsible for safe operations, the report stated.
The investigation identified several reasons why operations should have been brought to a halt when problems developed, but noted that "no individual on the Deepwater Horizon did so on April 20," 2010, the day of the oil rig explosion. The report also cited an "overall complacency" on the part of the Deepwater Horizon crew.
In a statement on Wednesday, BP said it agreed "with the report's core conclusion consistent with every other official investigation that the Deepwater Horizon accident was the result of multiple causes, involving multiple parties, including Transocean and Halliburton."
"From the outset, BP acknowledged its role in the accident and has taken concrete steps to further enhance safety and risk management throughout its global operations, including the implementation of new voluntary standards and practices in the Gulf of Mexico that exceed current regulatory requirements and strengthen the oversight of contractors," the statement continued.
The investigation found that BP was haphazard in identifying and communicating risks associated with the cementing operations.
It also said that recurring well-control events prior to the spill should have alerted the crew to potential problems. On March 8, the rig crew took at least 30 minutes to identify a "kick"-a potentially dangerous imbalance in pressure around the well. "The delay raised concerns among BP personnel about the Deepwater Horizon crew's ability to promptly detect kicks and take appropriate well control actions," the panel said.
Other official investigations also have concluded that the rig crew's decision to move forward with the well abandonment despite tests that identified potential hazards significantly contributed to the disaster.
Unlike other reports, however, the BOEMRE/Coast Guard investigation also includes a forensic analysis of the blowout preventer, which is meant to shut off the well in an emergency and serve as the last line of defense against a spill. The panel found that a heavy off-center drill pipe prevented the blowout preventer from doing its job.
"The buckling of the drill pipe, which likely occurred at or near the time when control of the well was lost, was caused by the force of the hydrocarbons blowing out of the well; by the weight of the 5,000 feet of drill pipe located in the riser above the BOP [blowout preventer] forcing the drill pipe down into the BOP stack; or by a combination of both," the report stated.
The report also made a number of recommendations to increase the safety of offshore drilling operations, saying that "stronger and more comprehensive federal regulations might have reduced the likelihood of the ... blowout."
It recommended requiring not one, but two barriers to seal each well. The use of both mechanical and cement barriers would "decrease the chances of blowout," the panel said. The report also recommended further testing of blowout preventers and improved drilling-inspection procedures.
The report documented more than half a dozen violations of federal regulations by BP and its contractors. "BOEMRE will be responsible for any regulatory action with respect to the violations," agency spokeswoman Melissa Schwartz said in an e-mail on Wednesday.
While spill liability is capped at $75 million under the Oil Pollution Act of 1990, BP has said it would not invoke the cap and would pay for all damages resulting from the spill. Still, the administration has asked Congress to pass legislation to raise the liability limit.
House Natural Resources Committee Chairman Doc Hastings, R-Wash., announced a full committee hearing on the report for Sept. 23.
"We need to hear from the investigators, but we also need to hear from those being investigated," said Rep. Ed Markey, D-Mass., in a statement. "Congress and the American people deserve a full hearing on the facts of this spill that affected millions of American citizens and countless small businesses on the Gulf Coast."
Wednesday's report and the new hearings do not guarantee congressional action on an offshore reform measure.
Senate Energy and Natural Resources Committee Chairman Jeff Bingaman, D-N.M., and ranking member Lisa Murkowski, R-Alaska, began work on a measure to boost offshore-drilling safety after the spill, but the legislation stalled in their committee earlier this year over a revenue-sharing provision that would allow coastal states to secure 37.5 percent of revenues from new energy production off their shores.