The Tauranga HDD crossing collaboration
In 2017, AJ Lucas, a trenchless installation specialty company, and M-I SWACO were challenged with drilling two horizontal directional drilling crossings under the Tauranga Harbor, New Zealand at lengths of 1,530 m and 1,560 m to allow for the installation of a 36-in. steel trunk sewer pipeline. The formations ranged from very soft silt, loose sand, stiff silt, and dense sand.
The Port of Tauranga is a natural harbor located in the Bay of Plenty on the North Island’s East Coast. It is the only deep water port between the cities of Auckland and Wellington. Since the drilling would take place under a highly sensitive marine environment, extra care had to be taken to prevent the occurrence of hydro-fracture or inadvertent returns into the harbor. Subsurface conditions were known to contain challenges to hole cleaning and borehole stability, and would require a fluid with exceptional rheological properties to complete successfully.