In May, three underwater power cables were laid beneath the harbour, replacing a submarine cable installed in 1947 and overhead lines installed in 1957.
Six pylons — two at Portobello, one on Goat Island, two on Quarantine Island and another at Port Chalmers — and three 1.8km lines, known as conductors, will be removed.
The aim of Aurora Energy’s crossing project was to improve power security for customers on the Otago Peninsula, project manager Ben Bulling said.
The decommissioning phase was complex and required months of planning and consultation with the community.
‘‘We need to ensure it is done incredibly safely, because it is an active harbour environment,’’ he said.
The plan was to disconnect the conductors from insulators on the pylons and winch them back on to drums from the Portobello or Port Chalmers side.
Once the conductors were removed, the pylons would be unbolted and flown by helicopter to a site at Portobello.
The pylons and conductors would be recycled as scrap metal, Mr Bulling said.
The lines would remain live until the morning of the decommissioning day.
The six steel grills which the pylons sit on would also be removed and the sites replanted.
The project was scheduled to be completed by the end of September.
