Crews expect a fire burning in a massive wood chip pile recovered from thousands of quake-damaged homes around Canterbury to continue burning for several days.
The extremely hot blaze may have started at the Burwood earthquake rubbish dump due to a spontaneous combustion brought on by excessive heat, and smoke has already been oozing out over surrounding buildings and suburbs for around six days.
Burwood Resource Recovery Park spokesperson Gareth James says his team plans to starve the fire before dousing it with soil and liquefaction.
"This type of fire in a wood chip fire burns very very hot, and the water essentially evaporates before it gets to the centre of the fire," he says.
"We're still allowing the recycled timber material to burn itself out because it's the best way of making sure it doesn't reignite in future but we're also covering it with soil, which is effectively smothering those remaining embers and starving them of oxygen."
The operation has been blessed with a southerly wind which has pushed the smoke out to sea and away from people living in the area.
Mr James says his team has spent a significant amount of time separating the treated and untreated wood from other metals at the dump and the initial plan was to chip the wood and provide it to a company for electricity production.
"It's a real shame that we went to all that effort to recover what is probably 30,000 tonnes of beautiful clean timber for reuse but it's unfortunately now gone."
Canterbury Medical Officer of Health Dr Raymond Pink says the risk to the public is low.
"Over the last few days the volume of smoke that's been produced has continually declined and so the risk to the public," he says.
"If the prevailing wind did send the smoke across residential areas, just staying indoors, keeping your windows closed, keeping out of the smoke is the most useful thing to do. It's recycled wood and it’s a mixture of both treated and untreated wood, so there's no concern of noxious material that may be a risk to public health in this situation."
The crews are building a five metre cap around the fire and will start pushing the dirt and liquefaction over hot spots when they cool enough to allow a vehicle to drive over safely.