Third-party damage (TPD) is any damage to underground infrastructure that occurs during work unrelated to the asset. In 2015, there were 10,107 TPD incidents in Canada causing over a billion dollars in estimated damage. TPD is the leading cause of failure for distribution gas pipelines; since distribution pipelines are generally located in areas with high population densities, TPD has significant safety and economic implications. In this study, a probabilistic model is developed to qualify the probability of failure of distribution pipelines due to TPD. The model consists of a fault tree model to quantify the probability of hit given the occurrence of third-party excavation activities and the methodology to evaluate the probability of failure given hit. Fault tree analysis (FTA) is a top down, deductive failure analysis method which uses Boolean logic to combine a series of basic events to analyze the state of a system. Earlier prior research demonstrated the ability of a FTA to quantify the probability of TPD occurring on natural gas transmission pipeline systems. These models allow for a quantitative analysis of preventative measures and, in conjunction with current practices, facilitate a predictive method to plan and optimize resource allocation for damage mitigation and emergency preparedness. The developed TPD model is validated using the data provided from a region in Southwest Ontario. The model will provide distribution companies with a practical tool to identify third-party damage hot spots, develop proactive third-party damage prevention measures, and prioritize damage repair activities using a risk-based approach.

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