An independent government investigation into the Macondo well blowout in April 2010 is warning that offshore drilling remains a dangerous proposition, in part because many operators may be using blowout preventers (BOP) that still have flawed designs.

Previous investigations of the disaster have concluded that the BOP attached to the BP plc-operated well failed. The incident killed 11 men and seriously injured 17 others after the Deepwater Horizon drilling rig was destroyed. Experts previously have said if the blind sheer ram (BSR) had been activated by the BOP at the time of the incident, it would have kept millions of barrels of oil from flowing into the Gulf of Mexico (GOM).

However, the U.S. Chemical Safety and Hazard Investigation Board (CSB) is disputing that argument. In the first two volumes of a draft report issued Thursday in Houston, investigators said the BOP did in fact activate the BSR, but not enough. A flaw in the BOP design — the same design still used by hundreds of operators in the GOM and worldwide — likely led to the oil spill.

“The findings reveal that pipe buckling can occur even when a well is shut-in,” which “could render a BOP inoperable in an emergency,” said CSB investigator Mary Beth Mulcahy.

CSB conducted interviews and collected nearly one million documents from 24 companies and other entities.

“Our investigation has produced several important findings that were not identified in earlier examinations of the blowout preventer failure,” said lead investigator Cheryl MacKenzie. “The CSB team performed a comprehensive examination of the full set of BOP testing data, which were not available to other investigative organizations when their various reports were completed. From this analysis, we were able to draw new conclusions about how the drill pipe buckled and moved off-center within the BOP, preventing the well from being sealed in an emergency.”

The worst environmental disaster in U.S. history led to a six-month deepwater drilling moratorium in the GOM and launched a reform initiative covering offshore regulations across the United States. The former Minerals Management Service was dissolved and replaced by three government entities. The Bureau of Safety and Environmental Enforcement (BSEE) oversees safety and environmental integrity. The Bureau of Ocean Energy Management handles lease sales/permitting; and the Office of Natural Resources Revenue collects royalty payments.

BSEE enacted strict safety and environmental management systems guidelines and enhancing safety systems and inspections. Industry groups also responded, forming the Marine Well Containment Co. and the Center for Offshore Safety. Members are tasked with mobilizing assets for capping stacks and response vehicles. BSEE also partnered with the University of Houston, Texas A&M University and the University of Texas at Austin to create the Ocean Energy Safety Institute.

However, all of the safety initiatives in place don’t address the root cause, the report said. The BOP is the failsafe, and the device should prevent the loss of well control and a catastrophic offshore blowout.

“Although both regulators and the industry itself have made significant progress since the 2010 calamity, more must be done to ensure the correct functioning of blowout preventers and other safety-critical elements that protect workers and the environment from major offshore accidents,” said CSB Chair Rafael Moure-Eraso. The initial report “makes clear why the current offshore safety framework needs to be further strengthened.”

The Deepwater Horizon, owned by Transocean Ltd., was using a BOP that was faulty before it was deployed to the GOM, according to CSB. MacKenzie said “BP and Transocean lacked an effective management system” for the BOP, and the device as “not treated as safety critical.”

In its new theory of why the BOP failed, CSB said the drilling pipe in the well at the time of the loss of well control buckled because of a phenomenon called “effective compression,” which prevented the BOP from effectively sealing the well. The drill pipe then bent and warped, not allowing the BSR to effectively cut and seal it. Buckling likely was caused by pressure that built up as oil continued to flow to that portion of the pipe, even after the crew managed to shut in the well.

There also wasn’t enough attention given to the wiring in the BOP control system, according to investigators. Faulty wiring in one of two redundant controls for the BSR led to the controls opposing each other rather than syncing, said investigators. At the same time, battery power for one of the controls failed. The BSR was able to activate automatically, despite what other investigations have concluded. However, the buckled pipe prevented the BOP from performing its functions. Rather than cutting off the pipe as intended, the BSR squeezed the off-centered pipe, and oil flowed.

The flaw in some BOPs to seal a well because of a buckled or misaligned drill pipe probably exists in other BOPs, investigators said. Operators that regularly test and inspect systems may not be aware of the defect.

Gaps in federal regulation also exist. BSEE now requires testing and safety checks on BOPs, but “deficiencies identified during the failure analysis…could still remain undetected in BOPs currently being deployed to wellheads.” Investigators also recommended that the American Petroleum Institute (API) publish guidance “to establish an effective management system for critical elements.”

BSEE officials defended their safety regimes now in place.

“Reforms to offshore oil and gas regulation and oversight include an offshore regulatory program that supports standards that emphasize a culture of safety, the development of oil spill response plans, enforcement of approved leases, plans and permits, and investments in the latest scientific research to enhance safety, reduce risk and keep pace with industry technologies,” BSEE said in a written response. BSEE is updating its procedures governing BOP technology and management. It had expected to issue a proposed rulemaking by the end of 2013, but that deadline now is for sometime this year.

BSEE’s first chief, Michael Bromwich, who has been involved in the post-Macondo regulatory restructuring, also offered his take on the report.

“The report finds a niche by focusing in great detail on the deficiencies of blowout preventers and on improvements that can be made in the government’s performance-based safety regulations,” he said. “If this focus stimulates continuing discussion on these issues, the report will have served a useful purpose.”

In her remarks at the CSB meeting, API Senior Policy Adviser Holly Hopkins said “no incident is acceptable. Our industry takes every incident seriously. Continued vigilance is essential in helping to prevent future incidents.” CSB’s report only focused on the BOP, but it “fails to acknowledge the entire system and the systems-based approach that is essential for safe operations.”