Taharoa Buoy Relocation


Customer: NZ Steel Mining Ltd (Bluescope NZ Steel)

Location: Taharoa, New Zealand

Contract type:  Construct Only

Construction Period: 2 years


Ports & Coastal Solutions New Zealand & Pacific Islands

Fast Facts

  • 55,000 Man hours
  • 500m pipeline extension
  • 70nm submerged pipeline tow
  • 0 LTI's

New Zealand Steel Mining (NZSM) operates an iron sand mine at Taharoa, approximately 140 km south of Auckland. The mine processes iron sand into a concentrate, which is stockpiled and periodically pumped via fresh water slurry to an export ship moored 3 km offshore.

A Single Buoy Mooring (SBM) fixed to a six leg anchor spread, facilitates the export ship mooring and slurry line transition from seabed to ship. Replacement of the export vessel with a new, larger capacity vessel in mid-2012 required more sea room to manoeuvre into, and away from, the SBM.

The Challenge

The project was located in a remote, rugged west coast environment with subsea construction in a 30 m to 35 m depth range under restricted working weather windows. Visibility on the sea floor was often poor causing a reduction in productivity. There were also cultural and environmental factors and associated resource consent timing restraints.  Additional constraints included the requirement to work around NZSM’s six weekly export ship loading cycle, which could not be disrupted.

The Solution

As far as practicable, our construction methodologies maximised land preparation and minimised marine works to improve productivity. To resolve this, the pipeline extension was fabricated and assembled on the Port Taranaki Main Wave Break. It was then launched from the breakwater and towed 70 nautical miles to Taharoa where it was installed in one operation in late February 2012. Dive crews and vessels were based in Kawhia, providing safe refuge during inclement seas.

Key to Success

McConnell Dowell built the existing SBM in the early 1970s, demonstrating we are still the contractor of choice for complex marine works. Careful programming and contingency planning allowed us to deliver each phase of the works without interruption to the export ship loading schedule. Drawing on our experience, we drove value and quality through the supply chain to ensure all key milestones for project completion were met.