The burned area was 20 metres by 15m and contained steel belts from tyres, as well as the remains of over 100 tyres.
The fire took about 13,600 litres of water to fully extinguish.
Neighbours had told council staff Stewart had returned to the property the day after the burning and used a digger to bury the remains of the burned material.
Northland Regional Council said an estimated 40 cubic metres of waste had to be removed and disposed of in Northland’s Puwera landfill in mid-May this year, after “lime stabilisation” was done on the land to reduce the mobility of zinc in the waste.
But the land remains on the Hazardous Activities and Industries List.
Judge DA Kirkpatrick said the thick smoke and noxious fumes should make any person realise that burning tyres was unlikely to be permitted.
“Taking that one step further, a person using land for farming activities should recognise that burying the remains of such a fire could have adverse effects, including the leaching of contaminants into groundwater,” he said.
Judge Kirkpatrick said while the disposal of tyres was not a simple matter, the tyres could have been disposed of at the Kaiwaka transfer station, which would have cost $25 per tyre.
Meanwhile, Stewart’s lawyer stressed that his client had been co-operative with the council and had paid for cleaning of the roofs of his neighbours.
Stewart was initially fined $47,500 but was given a 5 per cent discount for his previous good character and efforts at remediation, and another 23 per cent discount for an early guilty plea - taking his fine to $33,250.