Management of oil spill contamination in the Gulf of Patras caused by an accidental subsea blowout

A methodology is presented and applied to assess the oil contamination probability in the Gulf of Patras and the environmental impacts on the environmentally sensitive area of Mesolongi – Aitoliko coastal lagoons, and to examine the effectiveness of response systems. The procedure consists of the following steps: (1) Determination of the computational domain and the main areas of interest, (2) determination of the drilling sites and oil release characteristics, (3) selection of the simulation periods and collection of environmental data, (4) identification of the species of interest and their characteristics, (5) performance of stochastic calculations and oil contamination probability analysis, (6) determination of the worst-cases, (7) determination of the characteristics of response systems, (8) performance of deterministic calculations, and (9) assessment of the impact of oil spill in the areas of interest. Stochastic calculations that were performed for three typical seasonal weather variations of the year 2015, three oil release sites and specific oil characteristics, showed that there is a considerable probability of oil pollution that reaches 30% in the Mesolongi – Aitoliko lagoons. Based on a simplified approach regarding the characteristic of the sensitive birds and fish in the lagoons, deterministic calculations showed that 78–90% of the bird population and 2–4% of the fish population are expected to be contaminated in the case of an oil spill without any intervention. The use of dispersants reduced the amount of stranded oil by approximately 16–21% and the contaminated bird population of the lagoons to approximately 70%; however, the affected fish population increased to 6–8.5% due to the higher oil concentration in the water column. Mechanical recovery with skimmers "cleaned" almost 10% of the released oil quantity, but it did not have any noticeable effect on the stranded oil and the impacted bird and fish populations. - Highlights: • A methodology is presented to assess oil contamination by a subsea blowout. • The methodology combines stochastic and deterministic oil spill simulations. • The probability of oil pollution in the Mesolongi – Aitoliko lagoons may reach 30%. • The effectiveness of available oil spill response systems was examined. • Dispersants reduced the amount of contaminated bird population to 70%. - The oil pollution probability in the Gulf of Patras and the environmental impacts on the nearby coastal lagoons are assessed and the effectiveness of oil spill response systems are examined.