Kulluk report out
USCG cites inadequate risk management in grounding of Shell drilling rig
The U.S. Coast Guard has published its report documenting the findings from its investigation of the grounding of the Kulluk, Shell’s floating drilling platform, in the Gulf of Alaska on Dec. 31, 2012.
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The report says that a series of events led to the grounding but that the most significant factor in the accident was the inadequate assessment and management of risks associated with a complex winter vessel movement in Alaska’s unique and challenging operating environment.
High-risk endeavorRear Adm. Joseph Servidio, USCG assistant commandant for prevention policy, commented on the importance of addressing risks in marine operations.
“In this case, the risks associated with a single-vessel tow by a new purpose-built vessel of a unique conical-shaped hull, with people aboard, in winter Alaskan waters where weather systems and seas are expected to rapidly develop, were extremely high,” Servidio said.
Referencing a section of the report that highlights the possibility of enforcement actions against Edison Chouest Offshore, the operator of the Aiviq, the vessel towing the Kulluk, and some members of the Aiviq’s crew, Servidio commented that he was most troubled by the significant number and nature of the potential violations of law and regulations.
“I will ensure that these potential violations are thoroughly investigated by the officer in charge, marine inspection, western Alaska,” Servidio wrote.
“We appreciate the thorough investigation and will take any findings seriously,” wrote Shell spokeswoman Megan Baldino in a press release issued on April 3. “Already, we have implemented lessons learned from our internal review of our 2012 operations. Those improvements will be measured against the findings in the USCG report as well as recommendations from the U.S. Department of Interior.”
December 2012The Aiviq, with the Kulluk under tow, set out from Dutch Harbor on Dec. 21, 2012, to deliver the drilling rig to a yard in Seattle for repair, following the end of Shell’s 2012 open water drilling season in the Beaufort Sea. On Dec. 27, while the vessels were transiting the northern Gulf of Alaska in heavy seas the towing hawser between the two vessels parted. Although the Aiviq succeeded in re-establishing a tow using an emergency tow line, all four of the Aiviq’s engine’s subsequently failed.
Multiple vessels, including a Coast Guard cutter, tugs and the Aiviq herself, with her engines repaired, made valiant attempts to save the Kulluk. But, eventually with the response efforts defeated by severe gales, heavy seas and breaking towlines, on Dec. 31 the Kulluk ran aground on the shore of Sitkalidak Island, to the southeast of Kodiak Island.
The Coast Guard report says that Shell had decided to move the Kulluk to Seattle because of the impracticality of carrying out needed repairs to the rig in Alaska. On Dec. 7, 2012, the company made the final decision to move the vessel, with the vessel being scheduled to enter a Seattle shipyard in February. The report says that several factors played into the timing of the move from Dutch Harbor, including forecasts of weather and wave conditions for the period December 2012 to February 2013. A belief by Shell that millions of dollars of property tax might be assessed on Jan. 1, if the vessel was in Alaska on that date, also influenced the timing decision, the report says.
The AiviqThe Aiviq, a new, extremely powerful, ice-class anchor-handling vessel, had been commissioned by Shell for its Arctic exploration program and had been delivered from the shipbuilder in April 2012. The Aiviq had towed the Kulluk from Seattle to Dutch Harbor in preparation for Shell’s 2012 drilling season, and had also towed the Kulluk during that drilling season.
But, according to the Coast Guard report, while conducting those towing operations the Aiviq had experienced a number of technical difficulties, including an engine failure and a “host of mechanical problems.” A list of major issues remained unresolved as the Aiviq prepared for the December tow south, the report says.
One concern was a design problem that, during storm conditions, resulted in seawater ingress to areas of the deck where fuel vents and electrical fittings are located, the report says.
Shackle lostIt became clear from the outset of the Kulluk towing incident that the towline between the Kulluk and the Aiviq parted because of the loss of a large shackle that linked two sections of the line. Since the shackle itself was lost at sea when the line parted, it has not been possible to determine a cause for the shackle failure, the report says.
But, prior to shackle failure, the pitching of the Kulluk in heavy seas had placed intermittent loads in excess of 300 tons on the towing system, according to records from the system’s instrumentation. The shackle had a 120-ton rating, a rating that should enable the shackle to withstand a load of 240 tons without distortion, and as much as 600 tons before breaking, according to the Coast Guard report. However, the report says that the load ratings of the shackles used for the Kulluk tow appeared to be lower than the ratings recommended by the U.S. Navy Towing Manual.
Loads of more than 300 tons on the shackle immediately prior to the shackle failure suggest metal fatigue as a “significant contributor” to the failure, the report says.
Fuel contaminationApparently the failure of the Aiviq’s engines after the towline-breakage incident resulted from the internal corrosion of the engines’ fuel injectors, probably as a consequence of seawater contamination in the vessel’s fuel. The suspicion is that seawater had entered the fuel tanks through the tank vents, probably on numerous occasions prior to the engine failure, as a consequence of the design problem in which water could reach the vents during storms.
Although the Aiviq carried several spare injectors, the vessel only had sufficient spares to fix one engine, resulting in a need to procure further injectors from various parts of the United States and airlift them to the vessel.
Long list of factorsThe report provides a long list of factors that contributed to the Kulluk incident, including severe weather and the Kulluk’s unusual conical hull design, in addition to the technical issues associated with the shackle failure and the Aiviq’s engine problems. There were failings by the Aiviq’s crew in properly handling the tow, probably in part because of a lack of experience in carrying out a tow of this type in winter conditions in the Gulf of Alaska, the Coast Guard report says.
However, the report does commend the crews of the Aiviq and the other vessels involved in the Kulluk incident for their skill and resourcefulness in dealing with the emergency.
Inadequate planBut the report severely criticizes Shell’s towing plan, saying that the plan was inadequate for a towing operation across the Gulf of Alaska in the winter, had not been adequately reviewed, did not address the role of the master of the Aiviq in the towing operation and lacked proper contingency planning.
Reliance on a single towing vessel, the Aiviq, was ill advised, especially given the severe weather anticipated on the tow route. And the mechanical and design deficiencies that had been identified in the Aiviq should have precluded the use of this vessel for this tow, the report says.
The route used for the tow, although selected to remain within range of a land-based helicopter, should an emergency arise, did not provide sufficient sea room for launching an effective response prior the Kulluk drifting into dangerously shallow waters. And despite the expectation of severe weather along the tow route, the tow planners had not appreciated the overall risks involved in the tow — no formal risk assessment was conducted, the report says.
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