Risk Reduction Measures Applied to Horizontal Directional Drilling of a Complex Pipeline River Crossing in Canada

In August and September of 2003, Terasen Pipelines (Trans Mountain) Inc. successfully completed the Horizontal Directionally Drilled [HDD] replacement of it’s NPS 24” pipeline crossing at the Fraser River from Surrey to Coquitlam in southwestern British Columbia. The pipeline replacement was necessary to mitigate the high seismic risk from liquefaction induced lateral spreading of soils on the north and south shores of the Fraser River. The high level of urban development and the close proximity of major linear infrastructure on both sides of the river created spatial restrictions which increased the complexity and risk of the HDD crossing. Measures to reduce construction risks and limit Terasen’s exposure to claims for changed subsurface conditions, environmental damage due to frac-outs, delays, pipe and coating damage, and inability to complete the crossing, were applied. Important strategies used during planning and construction of the crossing included: proper selection of the pipeline route and laydown corridor, site specific geotechnical investigation, HDD annular pressure monitoring, HDD electronic drilling recording, and a contractor pre-qualification process. The final result was that the contractors successfully drilled and installed the 1293m long HDD crossing over a period of one month, without incident. This paper presents the challenges and solutions implemented by the project team to bring the project to its successful conclusion.