But after the English Elm on Bedford St snapped near its base about 7.50am last Thursday, Queenstown Lakes District Council parks contract manager Adrian Hoddinott said the “decay” the tree housed had been exposed “to its full extent”.
The failed tree was estimated to be about 15m long — two main trunks impacted the roof of the house, thought to weigh upwards of 10 tonnes each.
The property was occupied when the tree came crashing down, but fortunately no-one was hurt, he said.
Allied Media can reveal the trees do not appear to have ever been resistograph tested — a process in which a needle is inserted about 30cm into a tree’s trunk to measure resistance, thereby detecting decay.
Mr Hoddinott said the council would instead typically use PiCus testing, involving sensors around the trunk to detect issues, along with a ‘Quantified Tree Risk Assessment’ (QTRA), which was visual.
It appears that had not ever been used on the Arrowtown trees, either.
And, despite Thursday’s failure, he said there were “no current plans to undertake any reactive assessments”.
The failed tree was one of 38, of varying ages, on the stretch of Bedford St between Buckingham and Suffolk Sts.
The last tree to fall there was in 2018, he said.
They were thought to have been planted in 1877 by the Arrowtown Borough Council and sat on the district plan as ‘‘heritage trees‘‘.
Due to their age, historical value and location, they were subject to annual inspections using a visual inspection, which essentially calculated the overall risk of harm by assessing what could be damaged and how often those targets were present, the size of the potential failing part, and the likelihood of a tree or branch failing within, for example, a year.
Additionally, the trees were on a three-yearly maintenance schedule.
Real estate website homes.co.nz estimates the value of the house at $1.88 million.
In a statement, the council said the tenants were provided with alternative, temporary accommodation and, because it was on council-managed road reserve, they were working with the property owner and their insurer.
“To date, we haven’t seen any evidence of further risk [of tree failures] in Arrowtown or elsewhere in the district,” the statement said.
Mr Hoddinott, though, said in the wake of incidents such as last Thursday’s, “we always re-evaluate ourselves and our methods”.
“I think when events like this happen, it’s professional to reconsider your previous approach and test that.
“We haven’t landed on a view whether that [the PiCus test] would be used any more than we already do use it, as an additional tool.”
The owner of the Bedford St property declined to comment when contacted.
