Off-Property Release Likelihood Assessment of Liquid Pipeline Stations Through Barrier Analysis

Abstract Site containment is installed within pipeline stations as a protection barrier that prevents releases from traveling beyond the station boundary. However, with time barriers may degrade, for example berms may wear down due to vehicle traffic, containment valves may fail to close after decades of use, and/or facility patrol intervals may change. Correspondingly, there is potential that offsite release likelihoods may exceed company targets, which is especially pertinent for stations located in high consequence areas. Therefore, a methodology for evaluating the risk of an off-property release at facilities has been developed. This methodology quantifies both asset likelihood of failures, and the effectiveness of leak containment barriers inconsideration of operations (eg. drainage valve opening) and time dependent deterioration (eg. containment berm degradation). Review of facility drawings was conducted to inventory the station assets and catalogue the station barriers installed during construction. Field visits were then conducted to acquire information on leak barrier condition, berm and containment pond draining frequency due to precipitation events, and flow paths within the facility should a release occur. Subsequently, fault tree analysis was applied to determine the likelihood of off-property release. Asset specific probability of failures were used to quantify the basic events. Additionally, output gates determined the likelihood of off-property release via AND gates for redundant barriers and OR gates for dependent barriers. The likelihood of off-property release was quantified for each of the overland, spray, and below ground release modes. Environmental consequence was combined with this likelihood, to enable risk assessment. The methodology has been applied to multiple pipeline operator stations, and mitigations have been executed based on the results. This demonstrates that application of this methodology may identify whether off property release risk and reliability targets are exceeded, enabling informing of decision makers on mitigation priorities.