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What is Horizontal Directional Drilling?

Directional boring, also known as Horizontal Directional Drilling (HDD) is a method of installing pipes and conduits underground, along a planned bore path, with the least possible impact on the surrounding environment.

The process is used to install telecom and power cables, water and sewer lines, gas and oil lines, product pipelines and environmental remediation casings. It is also used for soil remediation and sampling, and for ploughing pipe beneath waterways, roadways, environmentally sensitive areas, or congested areas which would be disrupted by traditional piping procedures.

Advantages to the HDD process include lower cost, shorter completion times, reduced environmental impact, less traffic disruption, and the lack of a need for an access pit to be dug. Installations may be deeper and longer than with traditional drilling, and it is possible to 'steer' the pipeline along a set path. A transmitter located behind the drill head 'speaks' to a hand held receiver on the surface, ensuring that the proper path is being followed at all times.

The process begins when an HDD machine drives a boring head, which is attached to a hollow pipe, into the soil at an angle. Non-toxic drilling fluid, or "mud" helps the machine cut through the soil. As each length of pipe is pushed into the earth, a new one is connected behind. When steering, rotation of the bit and pipe are stopped, the angle of the bit is repositioned to the desired direction, and driven forward. The combination of forces of thrust and the stream of drilling fluid cuts a new conduit through which the pipe may pass. In unstable environments, a casing may be pushed down the hole to prevent collapse of the walls.

Once the bore has reached its desired length and the head has been steered back up to the surface, the bit is detached. If the desired diameter of the bore is larger than already completed, a reamer is attached, which will rotate along with the drill pipe during pullback to enlarge the hole. Once the hole is of sufficient size, the desired product pipe (or cable) is attached via a swivel to the reamer. Drilling fluid continues to lubricate the hole, while the swivel prevents rotation of the product pipe as it is pulled through the hole.

After pipe installation, the exit and entry points are excavated if necessary to allow connections to be made.