Practical Solutions for Mountainous Pipeline Construction: Mechanically Stabilized Earth Retaining Walls on a Western Canadian Transmission Pipeline Project

Abstract Pipeline construction in various mountainous terrains presents unique challenges. When the deeper burial is needed for mitigating against geohazards, the conventional methods relying on shallow ditches can become impractical. Trenchless methods may not always be technically feasible or cost-effective. A transmission pipeline project in Western Canada encounters steep slopes, rocky terrains, and numerous environmental complexities. Narrow construction corridors across streams and gullies prone to geohazard risks pose additional intricacies to the design and pipeline construction. This paper presents two case studies from this project about application of Mechanically Stabilized Earth (MSE) retaining walls as an alternative solution to achieve the hydrotechnical and geotechnical dominant design intent for mitigating geohazard risks in challenging terrains. The first case study is on rocky ground. Concrete box culverts were installed beneath the MSE wall and the pipe at a creek crossing to convey surface water across the Right-of-Way (RoW) while maintaining a drivable forest road atop the pipeline. The second case study is on steep and colluvium mantled hillside slopes. The design incorporated a combination of culverts, headwalls, concrete swales, and riprap armoring to mitigate the potential scour from debris slides and flows. This paper presents practical tools and best practices of applying MSE retaining walls tailored to pipeline construction to resolve challenges in rugged terrains, promote a cost-effective engineering approach and minimize environmental impact. The presented case studies provide adaptable solutions to ensure the long-term integrity and resilience of pipelines in geohazard-prone landscapes.