Horizontal Directional Drilling (HDD)
HDD Rig
Horizontal Directional Drilling (HDD) is a surface-to-surface trenchless method for the installation of pipes, conduits, and cables.  Construction is a three-phase process that consists of drilling a pilot bore, reaming the bore to reach the design diameter, and pulling the product pipe into the reamed bore.  Drilling fluids comprised of a mixture of water and bentonite are continuously pumped through the drilling equipment during all three phases, and are used to stabilize the bore, cool the cutting tools, lubricate the pipe string, and carry soil cuttings back to the surface.
HDD Rig  
During the first phase of construction, the pilot bore is drilled by a steerable bit whose position along the alignment is measured using a down-hole transmitter and a hand-held receiver that follows over the surface as drilling progresses.  In the second phase, a reamer is pulled back through the pilot bore one or more times in order to increase the diameter to a size suitable to accept the designed pipeline.  In the third phase, the product pipe is pulled into the reamed bore.
HDD Pullback
 
Product Pipe Pullback
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