Influence of Gradually Moving Slopes on Pipelines

The river valleys in the plains of Western Canada and the Northwestern United States are relatively young in a geological time scale and often have extensive landslide activity on the valley slopes. Depending on the geology, these landslides can have very low movement rates and show little or no visible signs of slope movement, but still be relevant for the integrity of pipelines. Pipelines installed in gradually moving landslide terrain are subject to some risk of damage, depending on the details of the installation and the level of activity of the slide. Directionally drilled pipeline installations can be particularly vulnerable to this type of slope movement relative to long term integrity. A number of case histories are reviewed that involved pipeline installations on slopes that were moving at slow but persistent rates. Measures were successfully implemented at several of the slopes to lower the risk to the pipelines. Many of these cases involved relatively low cost drainage measures that significantly reduced the risk of pipeline damage.