A HDPE pipe OD 355 mm (14“) had to be laid in a hilly forest. The height difference for this 170 m (560 ft) long HDD bore was 23 m (76 ft). The maximum depth to the surface was 14 m (57 ft).
Due to the high depth, this bore had to be done trenchless. The contractor Iwashita Sangyo from Hachiken Nishi-Ku, Japan decided to use his horizontal directional drilling (HDD) machine TERRA-JET 8522 S for this pipe laying job. Iwashita Sangyo has a long HDD experience. They own several HDD machines, the oldest TERRA-JET is more than 12 years old, and still in operation regularly. They used a three finger head for the pilot bore through the hard ground layers.