If a factor of 2% is applied for each of ten ships involved in the oil-combating operations, the ultimate fleet efficiency is 80% and the total clean-up costs increases by 10%. If a factor 4% is applied, the fleet efficiency is reduced by 40%, and HTS assay the clean-up costs increases by 25%, compared to the situation where the combating efficiency of ships is not reduced. However such drastic reduction of the fleet efficiency does not seem realistic, thus our choice for this parameter can be indirectly justified and its effect quantified. The nature of BBNs allows an efficient updating of this factor in light of new knowledge and evidences. This variable quantifies the amount of oil

that is expected to be collected before the oil slick reaches the shore. It indicates the amount of oil that the combating vessels will collect by multiplying the vessel’s reduced oil-combating efficiency with the time they have at their disposal. The variable has 13 states ranging from 0 to 50,000 m3, and find more its CPT is obtained using the following expression: equation(3) Amount of oil recovered offshore=C3ifC8·C12>C3C8·C21otherwisewhere C8 is Time to collect oil (hours); C21 is Reduced removal efficiency (m3/h); C3 stands for Amount to be recovered (m3). This variable expresses how much oil is still left in the water after

the oil-combating vessels have collected as much oil as possible in the time frame given. This variable contains 23 states, ranging from 0 to 50,000 m3, and its CPT is obtained through the following conditional Rebamipide expression: equation(4) Amount of oil washed ashore=0.01·C3ifC3⩽C5C3–C5otherwisewhere C3 is Amount to be recovered (m3); C5 means Amount of oil recovered offshore (m3). The expression means that if the

amount of oil recovered at sea is higher or the same as the amount to be recovered, there is no significant spill reaching the shore – we assume that 1% of the amount to be recovered is washed ashore. Otherwise, the fraction of what is left from the offshore clean-up is assumed to pollute the coast. We estimate that the oil mixture that reaches the shore and needs to be collected there contains 10% oil, 40% water and 50% other substances and materials; see for example Kaakkois-Suomen (2009). The amount of waste that needs to be collected is divided between the mechanical and manual clean-up methods. Their respective shares are determined based on m/t Prestige case, thus we assume 60% of the remaining spill being treated with mechanical methods and 40% is left for manual operations. Both nodes Amount of waste mechanical removal and Amount of waste manual removal exist in 21 states defined in intervals from 0 to 50,000 m3, and the CPTs are obtained by solving the following equations: equation(5) Waste(mechanical)=Amount of oil washed ashore·0.6/0.1 equation(6) Waste(manual)=Amount of oil washed ashore·0.4/0.