Tangoio fire: Faulty bulldozer exhaust likely sparked forest fire, report finds

A plane dropping red coloured fire retardant on the second day of the fire on Tangoio Settlement Rd, January 7. Photo / Warren Buckland

A Hawke's Bay logging company owner is surprised a report into a 400-hectare fire that consumed vast swathes of young forests at Tangoio has labelled his bulldozer's faulty exhaust as the likely cause.

The 46-page report into the January 6 blaze, that took 11 days and 300 people including volunteer firefighters and forestry staff to stem, was released to Hawke's Bay Today under the Official Information Act on Thursday.

The fire in Tangoio Forest, off Tangoio Settlement Rd, was reported to the Fire and Emergency Communication Centre at 11.43am.

It eventually burned through 195ha of one-to-five year old trees as well as pasture and scrub, and destroyed or damaged an estimated 500 metres of boundary fence.

The view from Napier on the second day of the fire. Photo / Warren Buckland

Wildfire Investigating Officer Donald Scott classed the fire as "accidental" and said the most likely cause of the fire were the carbon particles expelled from a defective exhaust system on a Komatsu D65EX-12 bulldozer owned by K & S Beard Logging.

That bulldozer was about 9am on January 6 moved from a location within a tree stand where it had been parked over the Christmas break.

"It is likely that these particles landed in fine dry forestry slash while the machine was being moved from under pine trees to the edge of Sutton Rd, a distance of about 100 metres," Scott said.

Burnt tree root indicating the fire travelled uphill. General origin area below burnt tree root. Photo / Don Scott

K & S Beard Logging owner Kerry Beard, which had the faulty Komatsu D65EX-12 bulldozer on site, said he was under the impression the fire was caused by a cigarette butt.

"The wind was blowing so hard that day the fire definitely did not start from a spark from the bulldozer."

Beard, who said he had not seen the report and had not been given access to it, said there was no point in arguing with the findings.

"We'll definitely get the exhaust fixed on the bulldozer, and get the bulldozers cleaned out."

The report's key evidence came from a mechanic who inspected the bulldozer on January 15, nine days after the start of the fire.

The mechanic found the exhaust system was in generally poor condition with a metal band partially covering a hole in the exhaust pipe.

There was evidence of exhaust gas leakage around this hole, with an area above the can blackened.

"The exhaust system on this machine is not in a very good condition," the mechanic noted.

"The muffler has a considerable amount of damage from corrosion. As well as this the external pipe and joining flex pipe are ill fitting and have no clamps to secure."

He also carried out a spark arrester test.

The first day of the fire off Tangoio Settlement Rd, north of Napier on January 6. Photo / Warren Buckland

A spark arrester is any device which prevents the emission of flammable debris from combustion sources, such as internal combustion engines, fireplaces, and wood burning stoves.

The machine failed the spark arrester test with more than 50 burns from carbon in the tester.

The first day of the fire off Tangoio Settlement Rd, north of Napier on January 6. Photo / Warren Buckland

Scott said in the report that as a result of the mechanic's inspection, he was confident the faulty exhaust provided the most likely source of ignition, which was then fanned by warm, dry, windy conditions.

Hawke's Bay principal rural fire officer Trevor Mitchell, on site for most of the 11 days the fire was burning, acknowledged the hard work of volunteer firefighters involved who had to walk 15km a day over steep, charred terrain in full firefighting gear.

"The conditions were such that the forestry crew could not contain the fire with the resources they had, so we had firefighters on site every day until the fire was contained."

Hole in exhaust pipe of Komatsu bulldozer. Photo / Supplied

Mitchell said the report's faulty exhaust finding highlighted the fact that it doesn't take a whole lot to start a huge fire.

"In dry conditions that's very common," he said.

"Fires on forestry land can quite often start due to maintenance-related issues in machinery, or rats, and the worst ones are starlings nesting in machinery."

Fire and Emergency NZ representatives have been approached for comment about whether they intend to prosecute as a result of the report's findings.

Overview of the area of origin before the Tangoio fire. Photo / Supplied