Performance of Terrain Mapping Estimation of Depth to Bedrock in Pipeline Construction Planning: A Case Study

Abstract Terrain mapping is the delineation of polygons with unique surficial geology, landforms and processes, and is often conducted at the start of a project to provide preliminary ground information, particularly in areas that have not been subject to significant development. Depth to bedrock, one of the attributes typically assigned to terrain mapping polygons, can be a key input in estimating rock excavation volumes through the design phase of a project. In this case study, design-level depth to bedrock estimation for three short new pipeline alignments routed through southeastern British Columbia are compared to detailed ground condition observations collected through construction. Possible causes of discrepancies are then discussed, leading to a review of the approach to conducting design-phase estimates for future projects.