ERA Acute-Implementation of a New Method for Environmental Risk Assessment of Acute Offshore Oil Spills

Abstract Energy companies, like Statoil and TOTAL conduct Environmental Risk assessments (ERAs) as part of their risk management processes to ensure acceptable environmental risk for all operations. In some parts of the world, ERAs are required by regulators to assess risk and as a basis for evaluating risk reducing measures. A standardized ERA Acute method has been developed, providing quantitative assessment of environmental impact and risk of acute oil spills covering four environmental compartments: sea surface, shoreline, water column and seafloor. The method usesoil drift simulations and Valued Ecosystem Components (VECs) data as input. Based on a selection of relevant oil spill incidents, impact and recovery timesare calculated for VECs in all compartmentsusingcontinuous functions. Several endpoints are provided including the "Resource Damage Factor" (RDF) combining the extent of an impact with recovery time, the risk matrix, and a risk comparison tool, e.g. for quantifying effects of risk reducing measures. The methodology has been benchmarked and compared to the current industry standard ERA used on the Norwegian Continental Shelf (NCS), the MIRA method (NOROG, 2007). The ERA Acute method has also been compared with data from the real spill incidents: Deepwater Horizon (Gulf of Mexico, 2010) and Exxon Valdez (Alaska, 1989). Estimated impact and recovery time of incidents, e.g. from post-spill monitoring of environmental impact and reconstructed oil exposure data from satellite have been compared to ERA acute calculations and oil spill simulations. Acknowledging that validation of the model is challenging, the results support the new impact algorithms, and are within the range of expected uncertainties related to field observations. The continuous risk functions better discriminate the effect of small spills and of mitigation measures compared toMIRA methodology, and details of the exposure mechanisms such as exposure time and specific behavior of surface species are also included. The validity and applicability of the new ERA Acute methodology are presented in the paper, including the benefits the industry obtains from a standardized methodology providing reliable environmental risk estimations.