Two large wildfires that erupted late last year in Tongariro National Park were both triggered by vehicles throwing hot metal sparks into roadside vegetation.
Fire and Emergency has released detailed investigation reports and cost breakdowns under the Official Information Act for the fires that started on November 8 and December 8 along SH47, which runs beside the national park.
While police have told the Herald the causes of the fires were accidental, it is only now that details of each can be reported.
The documents show that despite the fires occurring separately, both blazes began in strikingly similar circumstances, in almost the same place, and only one month apart.
The first fire was likely ignited on November 8 when a vehicle travelling west on SH47 lost its left‑rear wheel, causing the undercarriage to scrape along the road and produce high‑temperature sparks.
Witnesses recalled seeing people pushing a damaged vehicle about the same time 111 calls alerted authorities to a growing blaze.
Investigators managed to locate a vehicle about 400m from the site of the fire’s origin, on the opposite side of the road, hidden from sight.
When found, the vehicle did have four wheels fitted; however, the left-hand rear wheel was not correctly attached. There was damage to the underside of the vehicle “and evidence of metal components being subjected to high temperature”.
On the road, Fire and Emergency investigators documented drag marks stretching hundreds of metres and recovered metal fragments, many of which had been subjected to high temperatures.
The report concludes that dry tussock and scrub caught fire almost immediately and strong winds pushed the blaze deep into Tongariro National Park. By the time crews gained control days later, more than 3000ha had burned.
The cost of fighting the November fire was $995,330, including $811,298 for aerial suppression, as well as payments to volunteers, staff overtime, catering and travel.
Just 30 days later – and only hundreds of metres from the first fire’s origin – motorists reported a camper van towing a trailer south along the same highway, with the trailer “emitting a large number of sparks onto the side road from what appeared to be a major mechanical fault”.
It was later established that the mechanical fault was a bare wheel rim and broken axle after a tyre had blown out.
As the trailer was dragged along the road, sparks landed in roadside grasses. Drivers who passed the vehicle soon saw smoke rising ahead and discovered multiple fires.
Investigators later identified four ignition points spread over nearly a kilometre of SH47.
Those fires merged, burning through almost 300ha of tussock, flaxes and turpentine scrub – vegetation the report says was rated extreme fire danger that day.
The cause was again ruled accidental.
A cost breakdown shows the December fire has so far cost $438,139, including $376,869 in aerial operations.
Together, the two fires burned more than 3300ha and cost taxpayers more than $1.4 million to extinguish.
Ecologists examining the extensive fire damage have been encouraged by “green shoots” emerging amid the charred landscape.
However, a full recovery in the sub-alpine country will be slow, with some plant communities needing decades to re‑establish.
Remediation work is being managed by the Department of Conservation (DoC) and local hapū Ngāti Hikairo ki Tongariro, who have placed a 10‑year restorative rāhui (restriction) over the area to support cultural and ecological healing, restrict access and protect vulnerable species while the land regenerates.
The effort received a boost with a $3.5m commitment over five years, announced by Conservation Minister Tama Potaka in February. The funding, sourced from the international visitor levy (IVL), will pay for weed control and pest management.
Mike Scott is an award-winning visual journalist with more than two decades of experience telling stories across multiple media platforms.
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