A Risk-Based Approach to Managing Exposed Pipelines

Abstract Transmission pipelines are typically buried to meet the regulatory-specified depth of cover requirements to minimize their impact on the environment and the public. However, due to the erosion of the cover or grandfathered design, pipeline exposures are observed. Within North America, thousands of pipeline exposures are currently present (generally focused within swampy locations) as identified through depth of cover surveys. Exposed pipelines exhibit increased vulnerability to integrity and safety threats. For example: an exposure on a trail would be susceptible to being struck by an all-terrain vehicle. Correspondingly, a holistic approach is required to quantify the risks associated with exposed pipe sections to support site remediation decisions. Protective measures such as managing the condition of the coating, placing armored articulated mats, or cordoning off the exposed perimeter or relocation can reduce the vulnerability of exposed pipe sections. However, the selection of an appropriate and financially viable decision should be based on a thorough risk assessment that considers safety, environmental impact and cost-effectiveness. This paper presents an approach to assess the integrity and safety risks associated with exposed pipes. The model is based on the fundamentals of reliability engineering but also requires qualitative operator-specific inputs, which would be based on the knowledge of one’s system. The key inputs to the model include the probability of failure of integrity threats aggregated over the exposed length and the geospatial characteristics of the site. The model is then applied to a set of exposures in a case study, the exposures are risk-ranked, and the results are visually represented on a risk matrix. This type of assessment allows for a systematic approach to mitigation planning, ensuring that remediation efforts are directed toward sites with the highest risks. Both the threats and consequences of exposed pipe sections are described herein, with the potential that this may serve as a tool (with operator-specific calibrations) for decision-makers when prioritizing risk treatments at pipeline exposures.