Alliance Pipeline (Alliance), an integrated Canadian and U.S. high-pressure rich natural gas transmission system administers a Geohazard Management Program (GMP) which identifies, investigates, monitors and assesses sites subject to risks from geohazards. Within the pipeline industry, recent flood events have shown that pipelines with a seemingly adequate depth of cover can become exposed and fail in a single flood event. As such, it is important to understand which water crossings could result in a pipeline failure if the pipeline were to become exposed in a flood (termed vulnerability). Two complimentary methods were developed for evaluating the vulnerability of pipelines at water crossings. The first method is a mechanistic approach that compares the maximum allowable free span length (MAFSL) of an exposed pipeline to simple geomorphic properties of the water crossing. The MAFSL was determined by calculating the strain and fatigue limits of the pipeline from hydrodynamic loading and vortex shedding. The second approach is based on a statistical regression of historical pipeline performance, hydrotechnical inspection records and actual exposure rates to calculate a probabilistic estimate of pipeline vulnerability. Utilizing the developed approaches, the vulnerabilities were combined with probability of exposure values to provide an improved risk estimation of the water crossings. Further analysis shows the calculated likelihood of failure at the water crossings has no correlation to the depth of cover (DOC). This suggests that the designation of an arbitrary DOC requirement at water crossings is incongruous with risk management principles. Instead, the DOC at water crossings should be maintained at a safe level based on the specific hydraulic and geomorphic characteristics of the site.

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Over the last 15 years, BGC Engineering Inc. has developed and implemented a geohazards Integrity Management Program (IMP) with 12 major pipeline operators (consisting of gas and oil pipelines and of both gathering and transmission systems). Over this time, the program has been applied to the assessment of approximately 13,500 individual hydrotechnical and geotechnical geohazard sites spanning approximately 63,000 km of operating pipelines in Canada and the USA. Hydrotechnical (watercourse) and geotechnical (slope) hazards are the primary types of geohazards that have directly contributed to pipeline failures in Canada. As with all IMPs, the core objectives of a geohazard management system are to ensure a proactive approach that is repeatable and defensible. In order to meet these objectives, the program allows for varying levels of intensity of inspection and a recommended timescale for completion of actions to manage the identified geohazards in accordance with the degree of hazard that the site poses to the pipeline. In this way, the sites are managed in a proactive manner while remaining flexible to accommodate the most current conditions at each site. This paper will provide a background to the key components of the program related specifically to existing operating pipeline systems, present pertinent statistics on the occurrence of various types of geohazards based on the large dataset of inspections, and discuss some of the lessons learned in the form of program results and program challenges from implementing a geohazard integrity management system for a dozen operators with different ages of systems, complexity of pipeline networks, and in varied geographic settings.