New Zealand Oil Services Ltd (NZOSL), Z-Energy.

Civil contract requiring 2.4m deep trenching over 232m on the Otago Harbour foreshore. We were contracted to Wallace & Cooper Ltd to open trench for placing & welding pipe in situ between the port and Z energy’s holding tanks.

This line is used to transfer the fuel from ship to the holding tanks. All pipes were laid to within mm accuracy to allow a full penetration weld to an ANSI standard. All welds were fully x-rayed, then coated and wrapped in Polyken tape. The lines have an applied current corrosion protection system, meaning the installation must be perfect to avoid marking the insulation. Prior to commissioning the line, NSOL had an inspector travel down to test the pipe. He stated that the testing results were the best he had ever seen for that type of pipe, reflecting our attention to detail when laying and backfilling this pipe. 

This site presented many challenges including digging around unmarked services, trenching across industrial roadway while traffic managing logging trucks, dealing with variable running sands, groundwater, tidal fluctuations, as well monitoring all removed waste and water for contamination, and trenching beneath KiwiRail tracks.