The National Transportation Safety Board (NTSB) is naming Shell as being ultimately responsible for the grounding of the Kulluk ice-class mobile offshore drilling unit (MODU) in 2012 offshore Alaska, due to the company’s inadequate assessment of the risk for the towing.
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Tow vessel Aiviq, left, tows Shell’s conical drilling rig Kulluk before the Kulluk grounding in December 2012. Photo from pbase.com. |
The Noble Corp.-operated Kulluk was grounded in heavy weather near Ocean Bay, on the eastern coast of Sitkalidak Island off Kodiak Island on the night of 31 December 2012. The MODU was under tow by the ice-class anchor-handling tow supply vessel Aiviq, that departed Captains Bay near Unalaska, Alaska, 10 days earlier for the Seattle, Washington, area for maintenance and repairs. Four crewmembers on the Aiviq sustained minor injuries as a result of the accident, the NTSB said.
“No single error or mechanical failure led to this accident,” the NTSB accident report said. “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.”
According to the report, the Aiviq lost engine power at a critical point in the Kulluk’s tow. US Coast Guard investigators believe that the design of the fuel oil storage tanks’ common vent and overflow system was flawed and that these flaws led to the seawater contamination of the fuel tanks during the Aiviq’s transit during rough sea conditions.
“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,” the NTSB statement said. “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 report went on to say that 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 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.
The grounding of Kulluk
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Approximate course taken by the Aiviq towing the MODU Kulluk between Unalaska, Alaska, and the site of the grounding near the southeast coast of Kodiak Island. The Seattle, Washington, area was the intended destination. Image from National Geographic MapMaker Interactive. |
The Kulluk sustained substantial damage, a third party post-accident inspection found. Before the vessel was refloated, underwater portions of the hull were extensively damaged. Widespread damage to the vessel’s superstructure, electrical equipment, lifesaving and safety equipment, and interior and engineering spaces were endured.
Kulluk was carrying about 143,000 gallons of low-sulfur diesel oil and 12,000 gallons of other petroleum products at the time of the accident, however, no environmental damage was found due to the grounding, the NTSB said.
The 1773mi transit tow plan, according to the NTSB report, was expected to take 24.6 days at an average speed of 3 knots, 21.1 days at a average of 3.5 knots, or 18.5 days at an average 4 knots. The plan included to “turn into weather if possible and create as much sea room as possible, then proceed at a speed conducive with conditions,” should adverse weather were encountered.
Recovery teams were able to tow the Kulluck to Kiliuda Bay on 7 January 2013. ROVs arrived the next day to assess the hull.
Shell’s planned return to the Arctic
Shell is planning on returning to Arctic waters, to the Chukchi Sea, this summer after a two-year hiatus, using the Noble Discoverer and Transocean Polar Pioneer to drill two wells in a US$1 billion program.
“Ultimately, advances in technology provide the basis for improved safety, a reduced environmental footprint, and a more efficient operation. And these reasons give me confidence in our ability to explore responsibly in this region,” Ann Pickard, Shell executive VP, Arctic said at the Houston Offshore Technology Conference (OTC) in early May.
Also this month, the US Bureau of Ocean Energy Management (BOEM) granted conditional approval of Shell’s multi-year exploration plan for the Chukchi Sea. In April, the US Department of the Interior announced it had begun reviewing Shell’s Arctic plans following a record decision affirming Shell’s Arctic leases from the Chukchi Sea OCS oil and gas lease sale 193 from 2008.
Read more
OTC 15: Shell talks Arctic plans
BOEM approves Shell Arctic plan
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