Tauranga Southern Pipeline - Harbour Crossing

Abstract

The Tauranga Southern Pipeline Harbour Crossing is one of the largest HDD crossings completed in the region in recent times. It involved the completion of a 1560m long HDD crossing to accommodate a 914mm diameter steel casing. a DN800 HDPE pipe was then installed within the steel casing. The project required the installation of 1500mm steel casings on each side of the crossing to cross the shore lines and the HDD crossing then intersected into each casing. The drilling and downhole steering techniques were very complex due to a compound curve profile drilled to minimum bend radii. Reaming passes were up to 1425mm in diameter. We utilized our Herrenknecht HK400 ton drilling rig, 1000 GPM Brandt mud systems of each side of the crossing and 2 Gardner Denver PZ8 mud pumps. The project encountered a latent condition during the works that required multiple methodology deviations. The material encountered was assessed to be a 53,000 year Totara tree. Despite these challenges, the project was able to be successfully delivered without any health, safety of environmental incidents. This will address the high complexity of the project, the significant engineering phase of the works, the latent condition encountered and resolving the methodology so that the project could be successfully completed.