Through its experience with managing pipelines in the varied terrain of North America, Kinder Morgan Canada (KMC) is very aware of the effect of the geologic environment on its pipeline infrastructure. KMC’s Natural Hazards Management Program is one of the key tools for managing the risk to pipeline infrastructure.
This Program has helped define the current state of practice and includes annual field assessments along each of KMC’s pipeline systems at locations where river erosion or ground movement, such as landslides, are active or potentially active. The Program includes regular site inspections, detailed site studies, monitoring, and mitigation, and involves close work with specialised professional geoscience, engineering, and environmental consultants, who are experts in geohazards such as river erosion, landslides and seismic events (primarily earthquakes).
While river erosion and, to a lesser extent land slides, are relatively more common events, earthquake triggered geohazards, by contrast are episodic and relatively less frequent; with South-Western BC as the most seismically active region in Canada. Geohazards triggered by earthquakes include ground shaking, vertical settlement, and lateral ground displacement.
Major earthquakes around the world, including recent earthquakes in Alaska, Japan, New Zealand, Peru, Taiwan, and Turkey, have shown that ground shaking poses a relatively lower likelihood of causing damage to buried transmission pipelines if they are constructed in a manner similar to the existing Trans Mountain Pipeline, or what would be expected for the proposed expansion pipeline. The likelihood of damage to transmission pipelines from vertical ground settlement is also relatively low because transmission pipelines are relatively straight, with inherent flexibility, and typically do not have complex pipeline geometries that can be susceptible to seismically induced vertical ground displacement.
The most significant earthquake triggered geohazard that the pipeline(s) is exposed to is horizontal ground displacement from landslides and liquefaction induced lateral ground displacement (known as lateral spreading). Understanding potential location, estimated frequency, and magnitude of the potential lateral spreading is sought by designers and operators of any infrastructure in seismically active regions.
As with all organizations with infrastructure exposed to seismically triggered geohazards, KMC's objective to reduce the seismic risks to the existing Trans Mountain Pipeline is on-going and includes several investigations and major construction mitigation measures including:
- A system-wide qualitative assessment of earthquake hazards along the pipeline from Hope to the Burnaby terminal.
- Replacement of the Fraser River crossing by horizontal directional drilling to minimize exposure of the pipeline to seismically triggered lateral spreading.
- Characterization of potential earthquake triggered landslides at select locations along the pipeline.
- Preparation of an Earthquake Action Protocol to rapidly prioritize locations for pipeline inspection following an earthquake. This also includes procedures for shutting down and isolating the pipeline in the event of a serious earthquake.
Further seismic assessments along the proposed Trans Mountain Expansion Project corridor and existing Trans Mountain Pipeline will include:
- Site specific assessment of seismically induced ground deformation. Cohesionless soils, such as sands and low plastic silts, may be susceptible to liquefaction while cohesive soils, such as high plastic silts and clays with low undrained strength can be subject to cyclic softening. For soils susceptible to liquefaction or cyclic-softening, the loss of strength during or immediately following an earthquake can cause ground deformations such as lateral spreading (horizontal ground displacement) or post-shaking settlement (vertical ground displacement). The seismic ground deformation hazards will be assessed at susceptible locations along the proposed pipeline corridor and the pipeline and infrastructure will either avoid the geohazard or be designed to accommodate these potential ground movements.
- Site specific evaluations for seismically induced landslide potential. The potential for seismically triggered landslides will be assessed along the proposed corridor and the results and mitigation will be incorporated in the pipeline design.
- Site specific assessment of seismically induced ground shaking. When seismic waves travel through the soil and rock, locations along the earthquake propagation path and the pipeline are subject to shaking. An assessment of the predicted motion and additional strains that could be applied to the proposed expansed pipeline will be conducted and the results incorporated into the pipeline design.