Enbridge Pipelines Inc. has operated a 324 mm diameter, 870 km crude oil pipeline from Norman Wells, Northwest Territories to Zama, Alberta since 1985. This pipeline is the first completely buried oil pipeline constructed within the discontinuous permafrost zone of Canada. This pipeline was constructed over two winter seasons, and since 1985 has transported roughly 200 million barrels of crude oil to southern markets without significant interruption. This paper will review the design, construction, and operational challenges of this pipeline through the past 25 years. Unique and innovative aspects of this pipeline include measures taken during construction to minimize thermal disturbance to the soil, insulating permafrost slopes to minimize post-construction thaw, operating at temperatures that minimize thermal effects on the surrounding ground, accommodating ground movement caused by frost heave/thaw and slope instabilities, and evaluating the effects of moving water bodies adjacent to the pipeline right-of-way. The use of in-line inspection tools (GEOPIG) has been valuable as a supplement to conventional geotechnical monitoring, for the evaluation and assessment the effects of ground movement to the pipeline. Finite element pipe/soil interaction models have been developed for selected sites in order to assess the potential for slope movement to generate strains in the buried pipeline that exceed the strain capacity. This paper will review new monitoring data and findings since previous publications. In addition, the implications of long-term trends of increasing ground temperatures and associated changes to the geotechnical and permafrost conditions along the pipeline route will also be discussed and are relevant to other proposed pipeline and linear infrastructure projects along the Mackenzie Valley.

This content is only available via PDF.
You do not currently have access to this content.