Safety Alert Issued After Kulluk Grounding
The U.S. Coast Guard has issued a safety alert regarding the towing of large drilling rigs and the importance of planning.
The alert refers to the 2012 Kulluk incident and the 2016 Transocean Winner incident in the U.K.
In late 2012, the conical drilling rig Kulluk, owned by Shell Offshore and operated by Noble Drilling, was under tow from Dutch Harbor, Alaska to Seattle, Washington, in heavy weather, when a series of circumstances resulted in the failure of critical towing gear. The primary towing vessel, the Aiviq, also suffered a loss of propulsion due to contaminated fuel shortly after the initial towing gear failure. As a result, the Kulluk drifted for four days despite many unsuccessful efforts to regain control of the rig. Ultimately the rig grounded off Sitkalidak Island, on December 31, 2012.
The planning for the tow has been called into question by accident investigators. The National Transportation Safety Board (NTSB) stated that no single error or mechanical failure 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 rig at a time of year with a known likelihood of severe weather conditions for reasons unrelated to operational safety. 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.”
The NTSB concluded that: “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.”
In early August of this year, a 17,000-ton semi-submersible drilling rig, the Transocean Winner, went hard aground on the west side of the Isle of Lewis, Scotland. While en route from Norway to Malta, its towing line from the vessel ALP Forward parted after encountering severe weather. This incident is currently under investigation by the United Kingdom’s Maritime Accident Investigation, and it could have similar causal factors to the Alaskan incident.
A final report from the Coast Guard’s Report of Investigation on the Kulluk incident included background and guidance on the following topics:
• Critical tows: Describes how to use a simplified risk assessment methodology to analyze aspects of a future tow operation thus establishing future safety and equipment requirements;
• Voyage planning/plans (as required by the Code of Federal Regulations): Provides a solid but expandable foundation ensuring consideration of variables capable of impacting an intended operation;
• Tow procedures: Addresses operational requirements; defines responsibilities of involved parties; and describes equipment parameters, tow motion limitations, and the importance of having key reference material available;
• Towing gear: Provides information from a technical and analytical perspective on all aspects of the entire range of tow gear, its identification, selection, testing, etc.;
• Tug and tow master: Provides information on the interactions, relationships, and responsibilities for all of the senior persons involved in the towing operation, including the Offshore Installation Manager (OIM);
• Marine Warranty Surveyor: Explores all of the important roles and evaluations this individual performs in an effort to minimize and eliminate potential risks for the tow; and
• Recommendations: Presents numerous proposals to various entities associated with towing processes.
These recommendations, together with the content from other sections of the report, collectively serve as an overview of best practices for high risk towing operations.
The Coast Guard strongly recommends the widest distribution of this information for consideration and inclusion into various procedural and safety management systems of towing industry associated companies.
The safety alert is available here.