Demolition experts will take out two "wedges" from the base of Port Kembla's 200-metre stack, one bigger than the other, to ensure it falls the right direction.
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Port Kembla Copper recently presented details of the planned demolition to the WorkCover Authority of NSW, responsible for final approval and for setting terms of the felling, including the exclusion zone.
The stack is intended to fall in a north-northeast direction, on the grounds of PKC.
PKC general manager Ian Wilson said the 14,000-tonne stack would likely break into two or three pieces before it hit the ground.
Hundreds of holes will be drilled in wedge shapes near the base, with the bigger wedge on the side it will fall.
The holes will be filled with solid explosives, each with their own detonator, and this area wrapped in a geo-fabric to stop pieces flying outward.
"The explosives are sequenced to get the correct felling action," Mr Wilson said.
PKC discovered asbestos in parts of the structure on March 2011, and afterwards shelved plans to fell it using explosive methods.
The plans were revived last month after talks with Precision Demolition's Sean Miller, who devised a method for extracting the asbestos, contained in 22 thermal expansion gaskets inside the chimney.
Mr Miller has modified a steel acrow prop that will be key in supporting layers of the chimney so the asbestos can be extracted before the felling.
More than 300 of the props will be set inside the chimney's inner layer, and sacrificed in the blast.
Mr Wilson said it would likely take at least three months to extract about 20 tonnes of asbestos waste in this way.
