Directional boring, commonly called horizontal directional drilling or “HDD,” is a steerable trenchless method of installing underground pipes, conduits, and cables. Directional boring minimizes environmental disruption. It is suitable for a variety of soil conditions and jobs including road, landscape, and river crossings.
Installation lengths up to 2,000m have been completed, and diameters up to 56” (1,200 mm) have been installed in shorter runs. Pipes can be made of materials such as PVC, polyethylene, ductile iron, and steel, as long as the pipes can be pulled through the drilled hole.
Directional boring is used for installing infrastructure such as:
- Telecommunications & Power Cable Conduits
- Water Lines
- Sewer Lines
- Gas Lines
- Oil Lines
- Product Pipelines
- Environmental Remediation Casings
It is used for crossing waterways, roadways, shore approaches, congested areas, environmentally sensitive areas, and areas where other methods are costlier. HDD is used instead of other techniques to provide less traffic disruption, lower cost, deeper and/or longer installation, no access pit, shorter completion times, added directional capabilities, and overall environmental safety.
The technique has extensive use in urban areas for developing subsurface utilities as it avoids extensive open cut trenches. Uncontrolled drilling can lead to damages of existing utilities, however; so, the HDD method necessitates that the operator has complete information about the existing utilities so that he plans the whole alignment in a way that prevents any damage to them. Different government agencies have established legislation to ensure safe work execution and to authorize such work in urban environments. Different trenchless-technology promoting organizations have developed guidelines for this technique in order to standardize of the techniques.