A key federal report puts ultimate responsibility on BP for the worst offshore oil spill in U.S. history and the deaths of 11 rig workers, especially regarding the cement seal that was put in place the day before the explosion that triggered the spill.

The report, released Wednesday, said in the days leading up to the disaster, BP made a series of decisions that complicated cementing operations, added risk, and may have contributed to the ultimate failure of the cement job.


Environmental disaster ((AP) )

BP's Deepwater Horizon rig exploded on April 20, 2010, unleashing an estimated 780 million litres of oil into the Gulf of Mexico before the damaged well was capped three months later.

The blast killed 11 rig workers.

The gush of oil caused extensive damage to marine and wildlife habitat, as well as to the Gulf's fishing and tourism industries.

Other companies also shared some of the blame, according to the report, which noted that rig owner Transocean, as owner of the Deepwater Horizon, was responsible for conducting safe operations and for protecting personnel onboard.

The details were contained in the final report from an investigation team of the U.S. Coast Guard and the agency that regulates offshore drilling. The panel held hearings in the year following the April 20, 2010, Deepwater Horizon tragedy. The Coast Guard-Bureau of Ocean Energy Management Regulation and Enforcement investigation was among the most exhaustive.

Other investigations spread around the blame rather evenly, faulting misreadings of key data, the failure of the blowout preventer to stop the flow of oil to the sea and other shortcomings by executives, engineers and rig crew members. The joint investigation team laid considerable blame on BP's shoulders.

The report said the decisions included using only one cement barrier and BP's choice to set the production casing in a location in the Macondo well that created additional risk of influx of oil or gas. The casing is a steel pipe placed in a well to maintain its integrity.


Crews battle the blaze on the Deepwater Horizon oil rig. ((U.S. Coast Guard/Reuters))

The panel said BP failed to communicate these decisions and the increasing operational risks to Transocean.

"BP, as the designated operator under BOEMRE 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," the panel concluded.

The panel recommended further changes to offshore drilling practices, including requiring at least two barriers to be placed in a well — one mechanical, and one cement. The Macondo well only had a single barrier, the cement seal at the bottom, so when the blowout happened the only thing to stop it was the blowout preventer. That didn't work, the panel says, because the kink in the pipe caused by the force of the blowout kept it out of reach of the safety device's shearing rams. The team also said BOEMRE should standardize testing procedures on oil and gas wells.

BP, Transocean and cement contractor Halliburton did not immediately respond to requests for comment.

Report points to failure in assessing risk

The report paints a dark portrait of the final hours aboard the Deepwater Horizon, where the workers in the most danger — on the drilling floor at the center of the rig — were unaware of the anomalies being detected by engineers looking at data coming from the well. The federal team also charges that BP made decisions blindly, without assessing risk, and in some cases skipping internal processes the company relied on to evaluate the potential dangers of decisions.

While this report and others blame BP for jeopardizing safety to cut costs, the federal panel went further and examined the 2009 performance evaluations of 13 BP employees involved on the Macondo well. All but one of the reviews cited cost savings when evaluating the employee's work.

In addition to the rig worker deaths, the resulting oil spill off Louisiana spewed an estimated 780 million litres of crude from an undersea well owned by BP. The disaster caused billions of dollars in damage to hundreds of kilometres of coastline and wreaked havoc on the Gulf economy.

The report pins the causes for the disaster on many of the same faulty decisions found by previous probes, including those by the president's independent oil spill commission, Congressional committees and the companies themselves. But it is likely to carry more weight in Congress, where Republican lawmakers in particular have said they are unwilling to adopt reforms until the federal investigation was complete.


An underwater video camera shows oil gushing from the blown-out well's riser pipe in June 2010. ((BP/Associated Press))

Since the disaster, the Obama administration has reorganized the offshore drilling agency and boosted safety regulations. But Congress has yet to pass a single piece of legislation to address safety gaps highlighted by the disaster.

While the federal investigative team lays blame on decisions made by the companies, it does not address the government's own role in approving some of the questionable decisions. The federal agency that oversees offshore drilling signed off on many of the calls made by the companies, sometimes in minutes, and accepted an outdated and erroneous oil spill plan for the well that discussed protecting species that did not even exist in the Gulf of Mexico.

Congressional leaders immediately scheduled hearings to discuss the report's findings.

House Natural Resources chairman Doc Hastings, a Washington Republican who has pushed legislation to vastly expand offshore drilling since the disaster, said he hoped the federal government's conclusions would give lawmakers a clearer picture about what happened.

"We have waited far too long for this report, but the committee is ready to take action," Hastings said. "I'm confident that with a far more complete reporting of the facts, we will be able to take a thoughtful approach to real reforms to ensure continued safe American energy production."