What is Directional Drilling?
Directional boring, also referred to as horizontal directional drilling (HDD), is a minimal impact trenchless method of installing underground utilities such as pipe, conduit, or cables in a relatively shallow arc or radius along a prescribed underground path using a surface-launched drilling rig. Directional Boring/HDD offers significant environmental advantages over traditional cut and cover pipeline/utility installations. The technique is routinely used when conventional trenching or excavating is not practical or when minimal surface disturbance is required.
Directional Drilling Entrance Pit
The horizontal bore begins with the directional drill bit entering the entrance pit. The entrance pit is used to contain and manage the drilling fluids. The directional drilling crew are in radio communication with each other throughout the entire process. The directional drill bit is tracked by a sonde, or radio detection device, housed within its extended connection to the directional drill pipe, the depth and pitch is sent to the surface and received by the walkover locating device. The locator then gathers and interprets the information and then gives directions to the directional drill operator on which way to steer the drill bit. An experienced directional drilling crew can navigate and steer the drill bit up, down, right, left, and a combination of varying degrees of each to drill the desired horizontal bore path. The drilling crew always can determine the exact depth and location of the drill bit.
The Pilot Bore, Reamer, & Conduit
A typical midsize directional drill uses a 4-inch drill bit to drill a pilot bore. The bore path is typically enlarged to one and a half size the conduit that is being installed. In this installation, the bore path must be enlarged to accommodate the conduit and a reamer is attached to cut a larger diameter hole. The reamer is simply pulled through the existing bore path to enlarge the hole. As depicted in this video, and as most directional drilling projects, very little of the normal city activities were interrupted during the conduit installation. After the bore path is enlarged, the conduit is simply pulled into place by the directional drill rig.
Directional Drilling Benefits
This method of installing conduits has many benefits that include less disruption of commercial activities, less disruption of traffic, less site rehabilitation, and directional drilling can also be used to avoid damage to wetlands, streams, and for river crossings.