Installation of High-Pressure Pipelines in Complex Topographical Settings Utilizing Microtunneling

Microtunneling is an underground method of constructing pipelines using a remotely controlled, laser guided, steerable boring machine to install a pipe or casing, commonly a reinforced concrete pipe, using pipe jacking techniques. Planning considerations, design, and execution of two-pass microtunnel crossings must account for the limitations, capabilities, and operating loads of both, the casing pipe and the carrier pipe to result in a cost-effective design that minimizes costs and construction risks. The paper will describe five recently completed two-pass tunnels for high pressure pipelines, ranging in length from ~120 m to several kilometers, completed as part of the Transmountain Expansion Pipeline in a wide range of geological and hydrogeological conditions while crossing critical infrastructure networks and environmentally sensitive areas.