For onshore pipelines transporting hydrocarbon products that remain in a liquid state after release, environmental damage and socioeconomic impact are the dominant concerns. It is reasonable to assume that the magnitude of impact from such a release event is, at least in part, a function of the volume of product released. Analytical models exist for estimating the release volume from pipelines as a function of the physical and operational parameters of the line, and the effective size of the opening at the point of line break. While the estimates of release volumes obtained from such models are an important component of risk assessments and serve to inform emergency response planning activities, it is also important to understand what historical data indicates in terms of actual release volumes and how they are affected by key pipeline attributes. This paper summarizes the findings of an analysis of product release events associated with the onshore United States (US) hazardous liquid pipeline network, as obtained from reportable incident data publicly available from the Pipeline and Hazardous Materials Safety Administration (PHMSA). The findings of the study suggest that, for major releases resulting from large pipeline openings, release volumes are correlated with line diameter; whereas, releases as the result of a leak are largely independent of line diameter. Based on this, simple models have been developed from which both the average release volume and the range of likely release volumes can be estimated as a function of the pipeline diameter and mode of failure. These simple release volume estimation models are useful for benchmarking exercises where the goal is to estimate expected or most likely release volumes for calibrating and/or validating more complex release volume estimation models, and for estimating worst-case release volumes for emergency response planning purposes.

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