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Directional Boring, or Horizontal Directional Drilling (HDD) is a technique of installing underground pipelines, conduits or cables from the surface along a prescribed bore path.

Directional Boring is the leading method for pipeline construction to date. This is because Directional Drilling can be installed without any disturbance to natural habitats and has the least environmental impact of any method of construction.

What is directional drilling used for?

HDD is used for time and resource conservative installation of various pipelines.  These pipeline applications include (most common examples): gas, sewer, water, oil, and power.  This process is particularly useful when operating in areas of dense population or residential areas when the temporary demolition of roads or property is more tedious and expensive.

Directional drilling is a three stage process:


Creating the pilot hole is the first step of the Directional Drill boring. The pilot hole is achieved either by excavation of a small diameter pilot hole. Depending on the condition of the soil the pilot is drilled along a predetermined alignment in which the path is selected by traditional methods.

The typical pilot hole on most large rigs is 4" but can vary depending on the soil conditions and rig size. Drilling fluid is pumped through the drill pipe to the drill head and rushed or pumped through a drill motor. The end of the Drill Pipe is to core the pilot hole. The drill fluid lubricates the drill stem and carries out the cutting to the surface, then recycled and re-injected into the drill stem. The pilot process can take several days, depending on the condition of the soil and may require changing of the drill stem or drill head.


Once the pilot hole has been completed, step two takes place with a reamer or hole opener and enlarged to an appropriate size to safely install the product lines. A reamer is pulled back and rotated while pumping drilling fluid to cut and remove solids to enlarge the hole. Pre-reaming speeds will vary depending on existing soil conditions and the amount of cuttings that are removed from the hole. (example: 42″ finish hole would be 3 to 5 different ream passes 14″, 20″, 34″, 42″)


The reamer is attached to the drill string and is pushed or pulled while rotating and drill fluid is pumped to the reamer through the drill pipe. The excavated soil is suspended in the drill fluid and then brought to the surface and recycled.

When the reamer is attached to the Drill string there will always be a drill pipe on both sides of the reamer allowing for the drill string to be in the hole at all times. The reaming process can take a significant amount of time depending on the condition of the soil.



After the desired hole has been achieved and the reamer has passed through completely, a mud pass or packer reamer will be done to assure that the hole is clean of all excavated material and that the drill fluid has filled the hole completely.



The final step is the pullback of the pipe within the pre-reamed hole. The drill rod and reamer will be attached to a swivel, which is utilized between the product line and the reamer to prevent any torsional stress from the rotating drill string being transferred to the product pipe. This is to keep the pipeline as close to neutral buoyancy. Most buoyancy control is done with pumping water into the pipeline through PVC pipe and checking the gallons pumped.


De Witt Trenching specializes in all types of underground utility work, and we take pride on being knowledgeable and efficient while in the trench.

Our experience with the installation, repair and replacement of utility service lines will ensure you get the job done correctly. You can trust our judgment and decades of experience when discussing the plan of action to solve your problem.

The following is just a selection of the type of underground construction, directional boring and trenching projects that we provide everyday. Whether you have a small or large scale project, at De Witt Trenching we have the resources and experience to get it done for you.

  • Road & Highway Boring

  • Residential Driveway Boring

  • Irrigation System Boring

  • Parking Lot Boring

  • Under House/Foundational Boring

  • Force Utility Relocation Boring

  • Riverbed Boring

  • Inter-duct (Conduit) Placement

  • Plant Extension & Repairs

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