Pipeline route selection and design is an iterative process by which one or more potential pipeline corridors are systematically narrowed from the general path of about 10 km in width to a highly specified 30 m to 50 m wide corridor. The process usually spans several years, and is frequently becoming increasingly complicated, requiring a multi-disciplinary technical and managerial approach that considers the political and regulatory process, environmental impact and permitting, project and industry economics, access, constructability, land acquisition, and terrain. Specialist technical contributions to the pipeline routing process include pipeline hydraulics, pipeline and facility construction, terrain/geohazards, and environment/archaeology. Problematic terrain and geohazards are two of several issues that need to be managed through the feasibility and design of a new pipeline project. As the project advances through Front End Engineering and Design (FEED) from feasibility to final engineering design and as the corridor narrows from kilometers to tens of meters in width, the level of detail required in ongoing terrain and geohazard investigations should increase to optimize the design process and match the increased detail being provided by other specialists. An idealized Four-Stage framework for managing geohazards and problematic terrain during pipeline routing and design is outlined in the paper. This framework has been founded on several international resources listed in the references and has, by necessity, been developed, tested, and refined by the authors over the last ten years on several large and small diameter pipeline projects in North and South America. Each of the 4 Stages is described and contains guidelines on project study scale, a target corridor width, the engineering design level, cost accuracy, and geohazard related engineering tasks and deliverables. This staged approach is provided as a road map to help guide all project participants including owners, project managers, engineers, scientists, and regulators to understand how geohazards and problematic terrain are managed through the pipeline routing and design process.

Terrain mapping is the process of the interpretation of aerial photographs, LiDAR and satellite imagery plus field based ground truthing to delineate and characterize terrain polygons with similar surficial materials, landforms and geological processes [1]. For new pipeline projects, detailed terrain mapping is usually completed at a map scale of 1:20,000 corresponding to ground accuracy, at best, of 20 m. Although typically used to support the forestry industry in planning and developing forestry operations in British Columbia, Canada [2], and despite the rapid advancements of remote sensing technology, the art and science of terrain mapping continues to be an essential. albeit somewhat forgotten, tool for new and existing pipeline projects in a variety of terrain settings. For new pipeline projects, a quality terrain mapping product has been be used to characterize ground conditions and support the estimation of design inputs for numerous aspects of pipeline routing and design [3,4]. It is the backbone of most terrain and geohazard related tasks on a pipeline project and it is useful through many stages of a project’s development [5]. At routing and feasibility stages of a project, terrain mapping can be used to efficiently identify geohazards to avoid and to allow comparison of the terrain between different corridor options. Later on at the early design stages, terrain mapping can be used to develop and maintain a geohazard inventory to support geohazard risk assessment and design through geohazards that could not be avoided [6], delineate areas of shallow groundwater where buoyancy control and construction dewatering maybe required, help estimate soil spring parameters to support pipe stress analysis, delineate areas of shallow bedrock to support construction cost estimates and planning [8], and to identify sources of sands and gravels that maybe used for pipeline construction. This paper is intended to re-introduce the ongoing benefits of terrain mapping for new pipeline projects and describe how terrain mapping can cost-effectively support a pipeline project through its lifecycle of feasibility, design, and construction. Examples of the benefits of terrain mapping for routing and design of two proposed transmission pipelines in northern BC are presented. This work will be of interest to project managers, engineers, scientists and regulators involved with routing, design, and construction of new pipelines projects.

When new pipelines are constructed, they often cross existing major infrastructure, such as railways. To reduce potential service disruption, it is a common practice to complete these crossings using trenchless technologies. Without proper methods and oversight in planning and construction, there may be serious safety and financial implications to the operators of the railways and the public due to unacceptable settlement or heave. If movement tolerances are exceeded, the schedule and financial loss to the railway operators could be in the millions of dollars per day. Recent construction of a new pipeline across the Canadian prairies implemented ground movement monitoring plans at 19 trenchless railway crossings in order to reduce the potential for impact to the track and railway operations. The specifics of the plan varied for each site and were based on the expected ground conditions, as well as permit requirements from the various railway operators, but typically included ground movement monitoring surveys, observation of the cuttings, recommendations for a soil plug at the leading edge of the bore casing, and frequent communication with both the railway operators and the contractors. For all crossings, the expected soil and groundwater conditions were obtained from pre-construction boreholes and confirmed during excavation of the bore bays. Based on the expected ground conditions, appropriate soil plug lengths, if required, were recommended. In general, fine-grained clay/silt-dominated soils needed minimal to no soil plug in order to minimize the potential for ground heave, while coarser-grained sand-dominated soils needed a longer soil plug in order to reduce the potential for “flowing soil” which would cause over excavation along the bore path. Prior to boring, surface monitoring points were established along the tracks to monitor for changes in the ground surface elevation. Additional subsurface points were installed for crossings where the potential for over excavation was higher. These monitoring points were surveyed before, throughout, and following completion of construction, and the frequency of the surveys was increased when the movement was nearing or exceeding specified tolerances. The effort to monitor and reduce the potential for ground movement was a coordinated effort between the geotechnical engineers, railway operators, and construction contractors. The purpose of this paper is to present the lessons learned from the 19 trenchless railway crossings, including the challenges and successes. Recommendations for ground movement monitoring are also provided to help guide railway operators, design and geotechnical engineers, and contractors during the construction of future trenchless pipeline crossings of railway infrastructure.