In the last 5 years in Canada, regulators have been requesting that new pipeline projects provide quantitative risk management of all credible geohazards involving the proposed pipeline corridor so it can be demonstrated that geohazards are being recognized prioritized and that adequate resources are being allocated and to minimize the impact of adverse consequences of pipeline construction and operation. Complete risk management includes risk analysis that identifies credible geohazards sites, estimates their annual frequency or probability of pipeline failure and, when combined with a consequence of pipeline failure, estimates the risk from each hazard. This paper presents a framework and methodology that quantitatively estimates the Frequency of Loss of Containment (FLoC) for several types of geohazards that meet the requirements for geohazard identification and frequency analysis components of risk analysis. This framework builds on an international geohazard management framework advanced in the last decade by the Australian Geomechanics Society, British Columbia forestry industry, used in geohazard management programs for operating pipelines and proposed pipeline projects in Canada. The framework provides a repeatable and defensible methodology that is intended to be scalable to accept inputs from feasibility level desktop studies, through field-based observations, and incorporate proposed mitigations. This updated framework was most recently implemented on a proposed large diameter transmission pipeline route crossing the varied terrains of Western Canada, the results of which have been adjusted for Owner confidentiality, but are presented to demonstrate the application of the methodology and the effectiveness of communicating the overall hazard frequency reduction as a result of applying site specific mitigations.

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.

Horizontal Directional Drilling (HDD) is increasingly being used as a technique to install pipeline through challenging conditions. With this increased use, several post-installation geotechnical issues have, quite literally, surfaced, often many months or years following the original installation. These issues include sinkhole development around the entry/exit points for the HDD operations and settlement of the surface above the HDD bore path. Both can be attributed to two major factors, those involving unfavourable ground conditions and those involving problematic installation procedures. Several examples of each of these factors are described along with mitigation measures designed to prevent both sinkhole and settlement from occurring following HDD installation. Case histories from two large HDD crossings are subsequently presented which illustrate the potential magnitude of these issues and the steps that are often required for repair; the first from a crossing of the Fraser River outside of Vancouver, Canada, and the second from a crossing of a major river in north-central Argentina. In both of these cases, large sinkholes formed behind the HDD exit points, resulting in property damage and possibly threatening neighboring utilities. Site investigation and design techniques implemented to minimise the potential for sinkhole development and settlement are discussed, and several remediation options used in the cases histories are presented.

Earthquake hazard management for oil and gas pipelines should include both preparedness and response. The typical approach for management of seismic hazards for pipelines is to determine where large ground motions are frequently expected, and apply mitigation to those pipeline segments. The approach presented in this paper supplements the typical approach but focuses on what to do, and where to do it, just after an earthquake happens. In other words, we ask and answer: “Is the earthquake we just had important?”, “What pipeline is and what sites might it be important for?”, and “What should we do?” In general, modern, high-pressure oil and gas pipelines resist the direct effects of strong shaking, but are vulnerable to large co-seismic differential permanent ground displacement (PGD) produced by surface fault rupture, landslides, soil liquefaction, or lateral spreading. The approach used in this paper employs empirical relationships between earthquake magnitude, distance, and the occurrence of PGD, derived from co-seismic PGD case-history data, to prioritize affected pipeline segments for detailed site-specific hazard assessments, pre-event resiliency upgrades, and post-event response. To help pipeline operators prepare for earthquakes, pipeline networks are mapped with respect to earthquake probability and co-seismic PGD susceptibility. Geological and terrain analyses identify pipeline segments that cross PGD-susceptible ground. Probabilistic seismic models and deterministic scenarios are considered in estimating the frequency of sufficiently large and close causative earthquakes. Pipeline segments are prioritized where strong earthquakes are frequent and ground is susceptible to co-seismic PGD. These may be short-listed for mitigation that either reduces the pipeline’s vulnerability to damage or limits failure consequences. When an earthquake occurs, pipeline segments with credible PGD potential are highlighted within minutes of an earthquake’s occurrence. These assessments occur in near-real-time as part of an online geohazard management database. The system collects magnitude and location data from online earthquake data feeds and intersects them against pipeline network and terrain hazard map data. Pipeline operators can quickly mobilize inspection and response resources to a focused area of concern.

Pipelines and other linear facilities that traverse mountainous terrain may be subject to rock fall and rock slide hazards. A system is required to determine which sites pose the greatest hazard to the facility. Once sites are ranked according to hazard exposure, a risk management program involving inspection, monitoring, contingency planning and/or mitigation can be implemented in a systematic and defensible manner. A hazard rating methodology was developed to identify and characterize rock slope hazards above a South American Concentrate Pipeline, and to provide a relative ranking of hazard exposure for the pipeline, an access road and operational personnel. The rating methodology incorporates the geometry of the right-of-way, estimated pipe depth, staff and vehicle occupancy time, failure mechanism and magnitude, and the annual probability of hazard occurrence. This information is used in a risk-based framework to assign relative hazard ratings within rock slope sections of relatively uniform hazard exposure. This paper outlines a general framework for natural hazard and risk management along linear facilities, describes the rock slope hazard rating methodology, and illustrates how the system was applied along a South American Concentrate Pipeline.