Land disturbance associated with the progressive expansion of a major pipeline and power corridor, along with extensive timber harvesting, triggered the reactivation of an ancient, 100 million cubic meter deep-seated landslide in northern Alberta. The landslide threatened six major transmission pipelines, and caused a loss of containment in one of the pipelines. The level of landslide activity and associated pipeline damage was surprising given the relatively subtle disturbances in relation to the massive scale of the slide. Given the very shallow 4.5 degree slope inclination and the lack of any surface expression of distress over most of the slope area, this case history underscores the importance of considering regionally specific geological conditions within pipeline geohazard evaluations. An intensive, multi-pronged program was adopted to stabilize and manage the landslide, including a series of targeted surface and ground water control measures that produced an approximate 100-fold reduction in movement rates. This demonstrates that the sensitivity of slides in the region to subtle changes is a negative factor for triggering landslides, but can also be a positive factor for stabilizing them.

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