Wairoa submarine cable crossing

Location: Raupo, Ruawai to Tikinui, Pouto

Investment: $1.6 million

Start Date: June 2024

Completion Date: December 2024

Key people involved: Ben Bulling (Network Project Manager), Derryn Cooper (Contracting Project Manager)

Project partners: Nexans, Protectorshell, Seaworks, Te Uri O Hau, Atlas Cranes, Solid Civil Solutions

Northpower / Project case studies / Wairoa submarine cable crossing

Improving reliability at the edge of our network

In an exciting advancement in our work to upgrade our network and improve the reliability of electricity supply, Northpower installed two new submarine cables across the Wairoa River between Raupo, Ruawai and Tikinui on the Pouto Penninsula in November 2024.

The upgrade to our network means increased reliability in electricity supply to one of the most remote parts of our network, on the West Coast of the Kaipara Region.

Background

Around 50 years ago, two submarine cables were installed across the river with the help of a vehicle barge which no longer operates.

These cables are near end of life, and one of them had faulted, leaving only one old cable powering the Poutu Penninsula.

Surveying and working with Iwi

Northpower worked closely with Te Uri O Hau from the early stages of the project. The local iwi were instrumental in helping us with the cultural, archaeological, and environmental aspects of the project.

We completed surveys of the riverbed to gain information about the tides and river flows in the area to help decide the best installation methodology for the cables.

Installing the Cables

During the submarine cable installation in late November, we had to close the river to passing boats. This was advertised with boat ramp signage, social media posts, communication through Seaworks and the Harbourmaster, and letters to local residents of the area.

The installation over the scheduled three days, used a variety of machinery and divers. The cables were tied to buoys and were guided across the river using a winch to pull and a cable engine to push. Once across, divers cut the ropes tying the cables to the buoys, allowing the cables to sink and settle into place. Cast iron protector shells were also installed to help prevent any boat strike or accidental contact.

Once the cables were settled, they were commissioned in mid-December. On the Tikinui side of the river, a ground mount switch and ground mount transformer were installed and the overhead lines from Pouto Road to Tikinui Slip Road were removed.

Coordination and teamwork

This project required a lot of coordination between many contractors, including Northpower Network and Northpower Contracting, Seaworks (who specialise in installing marine cables), Solid Civil Solutions, TMNZ, and Atlas Cranes.