A branch or bark from a gum tree coming in contact with a power line "most likely" caused the Saddle Hill fire last year, a senior Otago Rural Fire Authority officer says.
Deputy principal rural fire officer Jamie Cowan concluded in his report an object, "most likely a branch or bark off the nearby gum tree", came into contact with a recloser unit on a power line beside Morris Rd.
The unit failed, melted and started a vegetation fire below, he said.
Wind gusts on the day ranged between 60kmh and 90kmh.
"This was a very fast-moving and dangerous fire and had it occurred in summer, the results would have been devastating and dangerous to control, with serious harm a probability," Mr Cowan said in the report.
He recommended avoiding planting gum trees next to power lines and for vegetation "trim zones" to be maintained at all times to minimise the risk of fire.
In the report, Mr Cowan said landowners in Morris Rd, next to where the fire started, had owned their property for about two years and never had any contact with an electricity network about trimming vegetation near power lines and no trimming had happened during their tenure.
The landowners who the Otago Daily Times believes own the gum tree stand declined to comment when contacted yesterday.
Anyone who had power lines on, or near, their land should contact their lines company to get a clear understanding of who was responsible for the trim zones, Mr Cowan said.
In the report, Mr Cowan said trimming of the tree stand near the recloser had been carried out at some point to keep vegetation clear of the power lines.
"However it is obvious that this practice has not been kept up to date, as vegetation was within 500mm of touching the power lines in multiple places. The ‘trim zone’ has not been maintained. However, in this case, I was unable to determine if this has likely contributed to the event that has caused this fire," Mr Cowan said in the report.
After the report was completed, the authority was fully reimbursed for the cost of fighting the blaze by the National Rural Fire Authority.
The NRFA could seek compensation if it believed a party was responsible for the fire.
NRFA rural fire manager Russell Barclay, of Dunedin, said no parties would be held responsible for the fire and no compensation would be sought.
Otago Rural Fire Authority principal rural fire officer Stephanie Rotarangi, who instructed Mr Cowan to complete the investigation, said conclusions could not be drawn from Mr Cowan’s observation of vegetation trims not being maintained.
"You can’t draw conclusions unless the evidence is there ... there was evidence the lines were hit but we couldn’t find what it was ... if you could see one of those branches had torn off in the wind, or was still there, then you can start to draw conclusions, based on the evidence."
Power companies and landowners were jointly responsible for trim zones, Dr Rotarangi said.
Power companies tended to do the first trim free and then it was the landowners’ responsibility.
"This was not a simple matter of vegetation in a trim zone falling over and impacting powerlines. If we had a situation like that it would have been quite easy to have found who was responsible. This was a matter of a particularly windy day with ... debris blowing around and travelling quite long distances."
Lines companies, such as Delta’s electricity network Aurora Energy, were responsible for checking trim zones, she said.
But if vegetation was near power lines, landowners and the public should contact the lines company see if vegetation trimming was needed.
Delta general manager asset management Derek Todd yesterday reminded landowners of their responsibilities to maintain trees clear of power lines "to reduce the number of unexpected power outages and [to] keep everyone safe".
