Horizontal directional drilling (HDD)

HDD (Horizontal Directional Drilling) is the process used to install utility services underground along a designated bore path over a set distance. It is mainly used when open cutting the same area is either to costly or not possible due to site limitations and/or restrictions such as environmental considerations.

The HDD process has been used to drill under rivers, roads, railway lines, mountains and buildings. A pilot bore is drilled under these objects to an exit point. A transmitter in the drill head is used to pin point the exact position of the drill head, then the drill head can be steered in what ever direction is required. The drill head is removed at the exit pit and a hole opener (reamer) is fitted to the drill string. The reamer is then reamed back towards the drilling rig and the required pipe pulled in behind the reamer.