The stack details
• Port Kembla Copper (PKC) indicated that approximately 10,600 tonnes of concrete, brick and steel reinforcing is contained within the stack.
• Approximately 92% consists of concrete, the remaining 8% consists of refractory brick which was used to construct the inner portion.
• The stack is constructed of an outer concrete weather shield and second (internal) concrete structural stack which surrounds an internal brick chimney
• The vast majority of the stack (greater than 99%) would not have been exposed to emissions. This is supported by brick sample analysis.
In the lead-up to felling
• The removal of sections of bricks and insertion of temporary props to allow removal of gaskets which contained asbestos. Twenty-one asbestos-containing gaskets were removed from the 23 levels of the stack between April and September 2013. A certificate verifying all asbestos gaskets have been removed was issued by a certified independent occupation hygienist. Tackifier was sprayed around the locations from which asbestos was removed.
• The area of the site where the stack is proposed to fall has been sealed with concrete, bitumen or a temporary Petrotac sealant (used as a final coat on road base).
The morning of demolition
• A 300m exclusion zone around the stack will be in place by 8am.
• Homes and businesses within the zone will be vacated and police will check on all premises prior to giving the all-clear to the demolition team.
• Sealed areas in the impact zone are swept, cleaned and wet down immediately prior to demolition.
• A combination of water cannons and long-cast sprinklers will be directed at the stack impact zone two hours prior to, during and at least two hours following demolition to minimise dust generation. This will create a water curtain where the stack will fall.
• The stack will fall to the north, in what is known as a ‘felling’ demolition.
• The stack felling is being carried out by Sean Miller from Precision Demolition.
• 934 holes have been drilled in the two outer layers at the base of the stack to allow placement of explosives. The holes also weaken the structure to facilitate the felling.
• The holes will be filled with a charge 150 millimetres long and 40 millimetres in diameter.
• Before the charges are detonated, they will be wrapped in chain wire and geo-fabric material to manage fly material.
• The explosives are sequenced to get the correct felling action.
• The felling of the stack will create overpressure from the use of explosives and ground-borne vibration from the actual impact of the stack hitting the ground. These impacts will be short-term in nature, lasting around 15 seconds.
• The detonation will blow out a wedge at the base of the stack on the northern side.
• The charges are designed to blow backwards into the stack. Charges at the front will be blown first, followed by the others in a decreasing ring around the base.
• As the structure begins to fall, a final ‘‘cracking charge’’ on the side opposite to the direction of the fall will be detonated.
• The demolition will make a noise comparable to a loud thunder clap.
• The land the stack will fall on is not flat but broken up into three tiers, has been sealed with concrete, bitumen or a temporary Petrotac sealant (used as a final coat on road base). The three ‘stepped’ tiers will spread vibration impacts and intensity rather than a single ‘hit’
• PKC is taking precautions to manage and monitor environmental factors including dust, vibration and noise.
• After the stack hits the ground, water spraying will continue to minimise dust.
• Unused buildings surrounding the fall line will offer further shielding. A representative from Precision Demolition will check all the charges have gone off before giving the all-clear.
• Once the stack has been felled, the rubble will form a single pile. Steel reinforcing will be removed and recycled if possible. The remaining material will be crushed. The rubble will be sprayed with water until crushing and removal is complete. Breaking up and crushing of the materials will not be conducted on windy days and on particular days when wind is blowing towards residential areas of Port Kembla.