But Aurora Energy operations and risk general manager John Campbell says the "pole-nailing" being done is a proven and effective alternative that is a well-tested and common practice.
Mr Healey said he was concerned ground conditions were not tested before pole-nailing, and the force required for pole-nailing would weaken the earth and poles around the nailed pole, meaning other poles were at risk of falling. This was an unacceptable risk to linemen and members of the public, he said.
"I am more than a little gutted that, after years of fighting to prove my case on this, Aurora have chosen to ignore the evidence and place the staff of their contractors at what I think is an unacceptable risk of fatal injury."
Mr Healey, whose revelations last year about Delta’s power pole practices brought the company and its parent Aurora Energy under public scrutiny, said he had warned against pole-nailing at the time he worked for Delta. Since leaving he had done 2500 calculations about the practice, which had been independently verified by two civil engineers.
The results showed that, except for very lightly loaded poles in the hardest ground types, the structures would fail through foundation collapse long before they reached the limits of the poles’ strength, he said.
He was concerned that poles which had been nailed had then had any warning tags taken off.
A pole nailed last week in Eureka St, Alexandra, had been red-tagged, but that tag was now gone. A pole nailed in Eureka St was beside one that fell on to a property last weekend, bringing live wires on to the roof of the house.
"This is exactly the concern I had, that the process of slamming the nail into an adjacent pole would strain a weak pole beside it, or it would break some below-ground support."
The Otago Daily Times has spoken to three Delta employees, who did not want to be named. One said Aurora had started pole-nailing to keep up with its pole replacement programme, another said it was being done to save money, and a third said Delta lineman had received little training about how to work on poles that had been nailed. He said staff had been told nailed poles were "theoretically safe to climb", but it was up to individual linemen to decide if they wanted to climb such a pole.
One said the practice was a good temporary solution that could extend the life of a power pole by several years, and that new methods of installing the nail into the ground used less force than other methods previously trialled.
However, he said it was possible the nailing of the pole in Eureka St had contributed to the falling of the adjacent pole.
He had concerns Aurora/Delta’s pole replacement programme was poorly documented, and not all poles assessed as red-tagged were in the replacement programme.
Mr Campbell said pole-nailing reinforcement was common practice in various countries, including Australia, and had been used in New Zealand for several years.
The process met the Australia/New Zealand standard and included an engineer assessing and confirming the upgraded strength of each individual pole as part of the reinforcement.
Aurora said it was investigating the Eureka St pole incident and WorkSafe had been notified.
Aurora’s Fast Track pole programme was well advanced in Central Otago, where 500 of the 1266 poles due for remediation in the region had been completed.
Mr Campbell did not respond to questions about whether ground strength or conditions around a pole were tested before the nailing process was done.
What is pole-nailing?
• A steel "nail" is inserted down the side of a power pole and strapped to it to strengthen and safeguard the pole, much like a stake would be driven into the ground and attached to a tree.
• The formed steel profile is about 6-8mm thick and 3m tall, with 1.5m above the ground and 1.5m below the ground when installed.
• The practice was investigated by Aurora Energy in about 2015 and some trials done, but the programme was put on hold in September 2016 because of concerns.
• Pole-nailing was trialled in Central Otago during the past month.
