A performance-based NaTech risk assessment methodology for hydrocarbon pipelines subjected to landslides

Distributed gas and oil pipelines often cross areas prone to landslides. According to the Eu Directive 2012/18/UE, known also as Seveso III, the risk to people and community served by the pipeline should be assessed. If the need is clear, the state of the art on available methods to solve this peculiar problem is limited. Methods to calculate NaTech risk according to a performance-based approach have already been proposed, especially for hazardous plants like refineries and oil & gas plant. Differently, a few similar approaches have been used for estimating the risk of consequences generated by a hydrocarbon material release from a pipeline subjected to landslide. In this paper a performance-based methodology to assess the mean annual frequency of release from pipelines for the transportation of hydrocarbons subjected to a landslide is proposed. This methodology employs the hazard curves of landslides, and the fragility curves of the pipelines defined in terms of permanent ground deformation. The content release is evaluated by using mechanical response quantities as local deformation as suggested in the literature. The proposed approach is validated through a representative case study of a pipeline for the transportation of oil crossing in a mountain region.