Probabilistic Risk Assessment for Contamination by Mineral Oil

The research topic has as its main objective the modeling of the flow of contaminant (mineral oil) following a road accident involving a heavy transport vehicle carrying 24 tons of CHEMOL pesticide, produced by the company Chemia S.p.A. of Sant’Agostino (FE). The target area is the ex-cave Olmi, currently used as a flood retention basin in the town of Calderara di Reno (BO), N-E of Bologna's Marconi airport, which is the final destination of the vehicle. Within this context, the thesis work concerned first of all the georeferencing and the study of an environmental report performed on the target area useful in the study of the hydrogeology of the soil and its stratigraphy. Subsequently, it was necessary to use the HSSM software to model the flow of contaminant in the soil. After this initial study, the Fault Tree (FTA) was built, the final event of which is the achievement of the target area, within a given time limit, a concentration higher than the limit given by the legislation. The failure rate of each basic event, which leads to the realization of the final event, was evaluated using values ​​derived from technical reports, with the exception of the event consisting in exceeding the concentration limit value in the target area. For the latter event, a Monte Carlo simulation was used, combining the values ​​of hydraulic conductivity and initial concentration of contaminant, which were the values ​​most affected by uncertainty. Finally, these values ​​were entered into the aforementioned HSSM software to evaluate the results. The probability of failure of this basic event was obtained by having the software compile a number of times equal to that of the possible combinations. The final calculation of the result, deriving from the constructed tree, was carried out using Boolean algebra, a method typically used in this probabilistic risk calculation technique. Below are elements relating to the techniques available for the removal of the pollutant.