Geotechincal Assessment for Mitigation of a High-Pressure Pipeline Across Active Landslides: Design of a Directional Bore in Southern California

Landslides are often a hazard to high-pressure gas transmission pipelines operating in hilly and mountainous terrain. Typical mitigation options include pipeline rerouting or removing the landslide from the pipeline, if possible. When rerouting or hazard removal is not a viable option due to terrain conditions or the size of the landslide loading the pipeline, directional bores can be used to place the pipeline beneath the active portion of the slope failure. As part of our study of the geotechnical viability of mitigation options for a pipeline impacted by coastal landslides, rerouting and landslide mitigation alternatives were fully investigated. Geologic interpretation of high-resolution, publicly available IfSAR and privately-flown LiDAR data were used to evaluate alternative routes around active and potentially active landslides. Geotechnical borings through the landslides ultimately provided sufficient information supporting directional drilling beneath the active landslides as the most efficient alternative, returning the pipeline to full service.