Shell is responsible for the 2012 grounding of a drilling rig offshore Alaska, The U.S. National Transportation Board (NTSB) has determined.

In its 14-pages long report, the NTSB has concluded that that probable cause of the grounding of the mobile offshore drilling unit Kulluk was Shell’s inadequate assessment of the risk for its planned tow of the Kulluk, resulting in implementation of a tow plan insufficient to mitigate that risk.

To remind, the incident happened on December 31, 2012, near Ocean Bay on the eastern coast of Sitkalidak Island off Kodiak Island, Alaska, while the rig was under tow by the anchor-handling tow supply vessel Aiviq, after it had completed a drilling season in the Beaufort Sea.

“I believe that this length of tow, at this time of year, in this location, with our current routing guarantees an ***kicking.”

The rig was on its way to Seattle for maintenance and repairs, to enable the rig to be ready for the upcoming 2013 drilling season, offshore Alaska.

According to the report, the day after departure, the Aiviq master wrote an e-mail to the Kulluk tow master stating, in part, “I believe that this length of tow, at this time of year, in this location, with our current routing guarantees an ***kicking.”

As it would turn out later, he was right as the Aiviq and Kulluk were hit by high winds and big waves, leading to power failures at Aiviq, broken tow lines, unsuccessful assists by several other vessels, and eventually grounding of the Kulluk.

Kulluk’s underwater portions of the hull were extensively damaged in the grounding, but the rig retained watertight integrity. Widespread damage also was noted to areas including the vessel’s superstructure, electrical equipment, lifesaving and safety equipment, and interior and engineering spaces. No environmental damage was found as a result of the grounding. Following the refloating, Kulluk was loaded on a heavy lift and transportation vessel, and shipped to China where it was scrapped, due to the amount of damage making it unfeasible for repairs.

Shell ultimately responsible for the accident

NTSB asserts that it was not a single error or mechanical failure that led to the accident. Rather, shortcomings in the design of a plan with an insufficient margin of safety allowed this accident to take place. The plan was created to move the MODU at a time of year with a known likelihood of severe weather conditions for reasons unrelated to operational safety.

Below is an excerpt from the report under which Shell is considered to be responsible for the grounding of Kulluk:

“Given the risks associated with this transit, including the likelihood of the tow encountering severe weather, Shell and its contractors, particularly Offshore Service Vessels, the operator of the Aiviq, who reviewed and approved the tow plan should have either mitigated those risks or departed at a time of year when severe weather was less likely.

For example, Shell and its contractors could have included additional tow vessels to the entire transit to reduce the likelihood of catastrophic results from a failure of the Aiviq or its tow gear. Redundancy is a necessary element of safety-critical transportation systems, and given the hazards of operations in Alaskan waters, those involved in the tow plan should have recognized and addressed the lack of redundancy.

“The series of failures that led to this accident began when Shell failed to fully address the risks associated with a late December tow in Alaskan waters"

The series of failures that led to this accident began when Shell failed to fully address the risks associated with a late December tow in Alaskan waters, and ended with the grounding of the Kulluk.

Although multiple parties were involved in the review and approval of the tow plan, the ultimate decision to approve and implement the tow was Shell’s. The dynamics of a single entity approving a go/no-go decision in the face of risks, with multiple parties involved, have been addressed in studies of previous catastrophic events.

This research demonstrates that, even with formal review processes involving multiple entities, the ability of parties involved in a decision to articulate and draw attention to risks is limited when a single entity bears ultimate decision-making responsibility and at the same time favors a particular outcome of the decision.

For this reason, Shell, as the organization responsible for designing, approving, and implementing the tow plan, is considered to be ultimately responsible for this accident.”

Source: www.offshoreenergytoday.com

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