Through our experience managing pipelines in varied terrain of North America, we are very aware of the effect of the geologic environment on our pipeline infrastructure. Our Natural Hazards Management Program is one of the key tools for managing the risk to pipeline infrastructure. 

Natural Hazards Management Program

This program has helped define how we do things today, including annual field assessments along each of our pipeline systems at locations where river erosion or ground movement, such as landslides, are active or potentially active. We regularly conduct site inspections, detailed site studies, monitoring and mitigation. We work closely with specialized 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 landslides, are relatively more common events, earthquake-triggered geohazards by contrast are episodic and relatively less frequent, with southwestern BC as the most seismically active region in Canada. Geohazards triggered by earthquakes include ground shaking, vertical settlement and lateral ground displacement.

Earthquakes and Pipelines

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 is expected for the proposed expansion pipeline. The likelihood of damage to transmission pipelines from vertical ground settlement is also relatively low because these 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 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, our objective is to reduce the seismic risks to the Trans Mountain Pipeline. We continue to review best practices and are taking the following measures:

  • 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.
  • At our terminal facilities, the “squat shaped” design of our storage tanks means they are unlikely to topple during seismic activity, and their steel construction makes them flexible enough to absorb earthquake shock waves. Each tank also has containment berms, or bays, which form giant empty pools to collect any spilled oil if a pipefitting were to leak. The holding capacity of each bay is about 10 per cent more than the capacity of each tank, ensuring ample space to contain any possible spillage. The bays are lined with an impermeable membrane for maximum spill protection. 

 We continually review all aspects of our operations and make improvements to incorporate seismic upgrades at our existing facilities

Considerations for Proposed Pipeline Expansion

Further seismic assessments along the proposed Trans Mountain Expansion Project corridor and existing Trans Mountain Pipeline 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 prone 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). We will assess the seismic ground deformation hazards 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. We will assess the potential for seismically-triggered landslides along the proposed corridor and the results and mitigation will be incorporated in the pipeline design for the proposed expansion. 
  • 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. We will conduct an assessment of the predicted motion and additional strains that could be applied to the proposed pipeline expansion and the results incorporated into the pipeline design of the proposed expansion.
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