Horizontal  directional drilling :

Horizontal underground directional drilling, commonly called horizontal directional drilling, directional boring, or HDD, is a steerable trenchless method of installing underground pipe, conduit, or cable in a shallow arc along a prescribed bore path by using a surface-launched drilling rig, with minimal impact on the surrounding area. Directional boring is used when trenching or excavating is not practical. It is suitable for a variety of soil conditions and jobs including road, landscape and river crossings. Horizontal Underground Directional Drilling (HUDD) occurs:

• on commercial construction sites;
• on residential construction sites; and
• on roadways, footpaths and verges.

Why is HDD used ?

Long-distance underground pipelines are built across open areas, such as rural farmlands and urban utility corridors. Typically, construction crews clear an approved route, dig a specially prepared trench, lower welded sections of pipeline into the trench, and carefully replace removed soil for the restoration process. Usually, this method is preferred for open area installation and can be completed in a way that minimizes environmental and stakeholder impact, even in sensitive areas. For large rivers or certain sensitive crossings, directional drilling is an appropriate and preferred construction method, depending on geologic conditions and other factors. HDD construction is considered suitable for large river crossings, extreme congestion (e.g. crossing rail yards), or other unique site-specific situations because it minimizes impacts on the area above the drill. Although land around the drill entry and exit locations is disturbed during HDD activities, it will be restored to its pre-drill state