Results of Environmental Risk Assessment Carried Out On Nearshore Gabon Installations Taking Into Account Environmental Sensitivity

Abstract

AbstractEnvironmental Risk Assessments (ERA) have been extensively carried out in 2014 by the Company (TOTAL) as part of the Technological Risk Assessment process. In that context it has been applied to nearshore Gabon pipelines and loading terminal located in the vicinity of Mandji Island and Cap Lopez. The approach used is consistent with the methodology already applied to far off-shore installations but in this case was applied for the first time to installations located at a few kilometers from the coast and using a validated set of hindcast current and wind data developed purposely for west coast Africa. The methodology applied takes into account the trajectory of potential oil spills and the probabilities that oil reaches any environmental resources. The tools used are 3D oil drift model (OSCAR) and exposure effect relations coming from the MIRA method developed in Norway. Four oil spill scenarios have been selected as representing most of oil spill cases requiring detailed environmental risk assessment on the basis of the technological risk assessment done on these installations. For each spill scenario, oil drift simulations were conducted in stochastic mode on the basis of 10 years historical wind and current data with 3km resolution. Quantities of oil and associated probabilities of presence were calculated for each cell of the model and comparison could be made with Argos drifter experiments in the case of one scenario. Shoreline habitats, turtles nesting beaches, seabirds, fisheries and mangroves have been selected as the key environmental resources to consider in this study. The results have been used to position the scenarios on the company risk matrix, assess environmental risk and address further needs on risk reduction measures. Results are discussed with some emphasis on the dominating role of current pattern in the area showing that environmental resources at risk are sometimes not the closest to the spill location. Validation aspects of the methodology related to current and Argos drifter experiment data are also discussed.