HDD is a trenchless pipe installation method through the bore hole that is drilled at underground. HDD is a recognized and often preferred method for installing all types of underground utilities such as water, sewer, gas, electric, and telephone. HDD is also well-suited for installing environmental remediation wells.

In the meaning of nowadays the 180 m long undercrossing with a gas high pressure pipe DN 100 made of steel of the river Pajaro near by the village Watsonville, California, in the year 1972, can be considered as the hour of birth of Horizontal-Directional-Drilling (HDD). This project was planned and successfully achieved by Martin Cherrington and his company, Firma Titan Contractors, founded in 1965.

 

Essential criteria of this totally novel technology concerning the construction of pipelines were adopted from the deep drilling technology of oil & gas and were improved for the special requirements of the controlled drilling in surface close areas.

Horizontal directional drilling is a technology allowing drill in three dimensions. It can be literally moved the drillhead up, down, left or right underground. This is accomplished by drilling a pilot bore into the ground at an angle and then leveling out at a specified depth. Once the proper depth has been reached, the pilot bore is typically advanced horizontally a specified distance and then back to the surface. In case of face with an obstacle at underground such as existing lines or very hard formations, profile can be modify to achieve the obstacle without pulling the drill stem out of the hole.

 

Once it exits the ground, the drill head is removed and a back reamer or expander is attached along with a swivel and the slotted well screen. It is then pulled back through the pilot bore to the drilling unit. To better understand it, let's take a look at the individual pieces of the process.