Environmental risk assessment has become a recognized tool to assess the impact of projects and production operations around the world. However, the methodology utilized to assess environmental risks range from simple workshops listing the various project or operational stages and potential environmental impacts to complex HAZIDS/HAZOP workshops. In most cases the workshop and risk assessment success can be based on the number and experience of the professionals present and the level of detail and time allowed for the assessment. The Bow-Tie methodology in risk assessment has been utilized in safety assessments for some time; however, it has not been utilized to any degree with environmental assessment.

The Bow-Tie method can significantly reduce the variability of results, which helps to increase the confidence in the findings from the assessment. The Bow-Tie method is a systematic approach to reviewing, selecting and ranking potential risks that provides a foundation for future efforts in control and mitigation. A procedure has been developed to assess environmental risk utilizing the Bow-Tie method similar to the approach applied in safety risk assessments. The Bow-Tie methodology has not been widely utilized in the environmental assessment of upstream operations to date. This paper reviews the process and results of such an effort.

The authors have utilized this method to assess the environmental aspects of an engineering design stage for an offshore platform and drilling program and discuss the lessons learned from this experience. Based on the results from this application, the Bow-tie method can be adapted for the evaluation of environmental impacts associated with early-phase development activities, including design phases, project start up and review of changes and new events, and startup operations.

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