Horizontal Directional Drilling, also called Directional Boring or Directional Drilling, is a trenchless technology which allows for the installation of pipes and conduits underground without disturbing or damaging the structures above. This technology makes it possible to place pipe underground without the need for digging up yards, landscaping, roads, sidewalks, parking lots, or wetlands. There is only minimal excavation required for Directional Drilling.

Entry and exit pits are selected and dug at each end of the job site. These pits will catch the drilling fluid used during the drilling process.

The directional drilling machine is set up at the entrance pit. A drilling head fitted with a bit is used to drill flexible rods into the ground, following a horizontal drill path that is planned and established for each project. An electronic sonde or transmitter is fitted into the drilling head. This sonde reports the depth, direction, angle, and pitch of the drilling head and is read using a tracking locator operated above ground by a technician. This technician then interprets the data and calculates the necessary values required to "steer" the drilling head in the correct direction. The locating tech reports these instructions to the drilling machine operator. Each job site is different, and while some are straight-forward, others require complicated steering and/or depth changes to avoid underground facilities and obstructions.

Once the drilling head reaches the exit pit, a reamer (if required) or the pipe itself is connected to the drilling head and pulled back through the pilot hole. In cases of large pipe, a reamer of 1.5x the pipe size is attached and used to expand the size of the pilot hole to accommodate the pipe.

The drilling fluids (which we call "mud"), a mix of water and bentonite clay, are an important part of the process. It keeps the drilling head cool and lubricated, fills and stabilizes the drilled pilot hole so that it does not collapse before the pipe is in place, and removes the cuttings produced by the drilling bit. This fluid is collected in the entry and exit pits, and is removed by a vacuum system throughout the project.