Case Studies of Scour and Erosion at Water Crossings

TransCanada Pipelines Ltd. (TransCanada) owns and operates over 38,000 km of pipeline facilities, geographically situated throughout Canada and portions of the USA. These facilities cross diverse terrain such as the Rocky Mountains in the west, the flat prairies of central Canada and the Canadian Shield in Ontario and Quebec. Within the complex geographic terrain are numerous hydrologic regions that contain over 2700 pipline crossings of creeks, rivers and lakes. Many of these crossings have been subject to some form of streambed degradation and coupled with extreme flooding events, have resulted in reduction of cover over the pipeline and/or exposed pipeline crossings. These hydraulic conditions can further threaten the integrity of an exposed pipeline crossing when subjected to vortex shedding, horizontal load or impact from floating debris. Historically 8 exposures have been identified and investigated in Alberta and 3 of them have been chosen as case studies for this presentation (the South Saskatchewan River, the Red Deer River and the Simonette River). Each case study will detail the following; historical events leading up to the incident, hydrotechnical analysis, the decision processes the design approach and implementation.