Rotorua investigation ongoing a year after fallen tree kills Trish Butterworth

A year ago today, Rotorua bore the brunt of a storm that left thousands without power, surface flooding and slips across the district, and 37 fallen trees and branches.

Among those, was the 23m tall "Spencer's Oak" on the corner of Arawa St and Amohia St, which split in two, crushing the car carrying Rotorua pre-school teacher Trish Butterworth, 56.

At 10.45am the tree, which was more than 150 years old, came down on to the Te Arawa House and blocked off Amohia St, where Butterworth was driving.

At the time of the storm, Rotorua Lakes Council acting chief executive Craig Tiriana said a February 2017 report recommended annual inspections, but it found no major issues with the tree.

"Following concerns from a local tree specialist in recent months about bracing in the tree, another inspection was done by the council's regular contractor. In late September/early October bracing was replaced and some branch reduction was also undertaken."

Police spoke to at least four witnesses for a fatality inquiry on behalf of the Coroner and closed the road to map the scene.

Area prevention manager Brendon Keenan said at the time, "we are going through all of the council records in relation to the tree ... Of course, we are working through it with structural engineers."

A year on, a Coronial Services spokeswoman confirmed the investigation was "continuing".

"This case is active before the Coroner ... and no decisions have yet been made in regards to a hearing."

Documents released by the Rotorua Lakes Council under the Local Government Official Information and Meetings Act showed concrete was poured into the tree.

A council-commissioned report in 2002 showed the tree was mostly in good health, but there was a "large cavity" in the main fork that had been partially filled with concrete and pumice.

At a council meeting a month after the tree fell, acting operations group manager Henry Weston described it as a "catastrophic failure".

He said pouring concrete into trees had been common practice in the past, but as time went on there was "general consensus that it just wasn't effective".

It was believed the concrete was poured before the council took over ownership of the tree, Weston said.

Butterworth's mother Pauline White told NZME last year that seeing old trees hanging over roads made her "shiver".

"I think the [Rotorua Lakes] council has done a very good job, they were co-operative and sympathetic, but I think the system needs to be a bit more ruthless when it comes to trees."

White said Butterwoth was "really happy" and "put her heart and soul into her job".

"She was my rock."

Butterworth's family did not want to provide further comment this week.