When constructing pipelines, it is not always possible or ideal to use traditional open-cut methods of installation. In these cases, such as when a pipeline route crosses a river or a major road, trenchless technology is used to install the pipeline with minimal surface excavation.

Benefits of using trenchless technology include reduced damage to roads and disruption to traffic; increased public and worker safety; and a number of environmental advantages, including minimised adverse impact on flora and fauna, reduced carbon emissions, and less pollution.

The most common trenchless construction method for transmission pipelines is horizontal directional drilling, which involves drilling a pilot hole beneath the sensitive area where an open trench cannot be made. The hole is then enlarged to the desired size during the reaming process, before the pipe is pulled back through the hole.

Another method is tunnelling, which uses a tunnel boring machine to create a hole into which the pipeline can be installed without disrupting the ground surface. A subset of this is microtunnelling, which uses the same method but on a much smaller scale. Microtunnelling boring machines (MTBM) are too small to have an operator and are thus steered remotely. Sometimes a jacking system will push the pipe in behind the MTBM in a process known as pipe-jacking.