Prediction of Exposure Risk for Buried Pipelines due to Surface Erosion

Abstract

Pipeline right-of-way maintenance activities face great challenges that have come from different climates, slopes, soils and other environmental conditions. Control of surface drainage and erosion is an important element in the restoration and maintenance of pipeline right-of-ways, since erosion can result in risk of pipe exposure and its consequences. Evaluation of this risk can be a powerful tool to ensure reliability of buried pipelines. The universal soil loss equation is used as a model to estimate the rates of erosion at sections of rights-of-way of a gas pipeline right-of-way near Vitoria city in southeast of Brazil. The confrontation of these rates to the actual pipe cover depths is used as a basis to derive a probabilistic procedure for determining the time period over which exposure may occur for a given level of uncertainty. Then, risk can be estimate as a product of the probability (or frequency) of product leakage due to pipeline exposure and the associated consequences of this event. Such risk definition is used to estimate results in an effective guideline to engineers, since it leads to the achievement of optimum and safe erosion control and superficial drainage system projects and results in efficient mitigation planning programs. The results obtained are very promising and show relevant correspondence with the erosion process and cover depth reduction identified on the right-of-way.