Major oil spills have the potential to become major environmental incidents. This paper aims to summarize the results of the study aimed at providing oil companies with more effective tools to help them better manage their environmental risks associated with the occurrence of major oil spills during offshore drilling operations. The latter is meant to be achieved by following a rigorous and systematic approach to the integrity management of environmental barriers and the performance of safety critical tasks in the same way the industry has long dealt with the management of integrity thereof.

The paper suggests complementing the approach contained in the IPIECA IOGP guidelines on oil spill contingency planning with DNV guidelines on environmental barrier management. This way the known cycle of ‘assurance and verification' will cover those barriers which are in place to mitigate the effects of major oil spills thus ensuring their availability and effectiveness when are called upon. This includes: a) the identification of environmental critical elements and tasks, b) development of performance standards c) identification of assurance and verification activities and d) the reporting of deviations to senior management levels and taking of corrective actions.

The paper introduces the Bowtie risk management methodology as a tool which supports the barrier management approach by linking technical risk analyses with safety management systems (SMS). This is thanks to its inherent strengths not present in other risk assessment methodologies such as event trees and fault trees. Last, but not least, the introduction of Bowtie methodology will facilitate understanding by all levels of the Oil Company of the role of the barriers in mitigating the effects of accident scenarios and their relationship with other barriers during the control of the accident scenario. The latter is realized through the motto that characterizes Bowtie methodology - ‘A picture paints a thousand words'.

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