There are two basic ways to construct a natural gas pipeline, trenching and boring.
Trenching involves digging a trench into which the pipeline is laid and covered by 36 inches or more of soil. During trenching, a temporary construction workspace is needed alongside the pipeline easement. Excavated soil is piled on one side of the trench and used for backfilling after the pipe is installed in the trench. The trench method is often used in areas where construction space is less restrictive.
Boring is commonly used when there is a need to cross underneath a surface feature, such as a road or stream, with minimal impact. A guided boring machine creates an underground pathway for the pipeline by drilling a bore from one side to the other. After reaching the opposite side, the machine pulls the string of pipe back through the hole it just created. Typical depths range between 3 - 60 feet underground. A long distance bore is accomplished using a method called horizontal directional drilling (HDD).