Horizontal Directional Drilling, otherwise known as HDD, is a trenchless method of installing underground pipe lines with minimal surface disruption. 
The HDD method utilizes a drill rig that is able to navigate a drill rod underground for extended distances. The diameter of the utility line may range from small diameter projects of 1" to larger diameter projects of 36" and larger.

Drilling is assisted with an environmentally safe drilling fluid. The drilling fluid is made up of primarily water and bentonite, a naturally occurring non-toxic clay mineral. The purpose of the fluids is to remove the cuttings, stabilize the borehole and act as a coolant and lubricant during the drilling process. 

Horizontal Directional Drilling allows the placement of underground utilities in limited-access, developed or restricted areas. Such areas include highways, freeways, parking lots, landscaped areas, or streams and rivers. Because the method is noninvasive, restoration in these situations is either greatly reduced or if not eliminated. This contributes to environmentally safe projects and can lead to project savings and enhanced public acceptance.
The HDD technique can be used in various ground conditions including hard rock, sand, silt and clay soil types.

This technology of horizontal directional drilling enables Precision Directional Boring to track and steer the drill head with the utmost precision around and under water, wet lands, existing utilities, roadways, parking areas, landscaping, retaining walls, steep embankments, and other obstacles that may be located below or above ground. 

The result of horizontal directional drilling is a greater degree of precision in placing the underground utilities without impacting the environment and the surrounding area. Alternate methods for underground utility installations include the traditional method of open dig trenching.