Waste

• Waste rock
• Tailings
• Other waste materials described in the section below called Recycling and reuse.

Read on to find out how this waste is minimised, recycled or reused.

Tailings and Waste Rock

Tailings is a mixture of water, chemicals and crushed rock from which the valuable copper, uranium, gold and silver bearing minerals have been extracted. It is pumped as a wet, mud-like slurry from the processing plant to the Tailings Retention System (TRS). The TRS is a complex system of tailings impoundments and evaporation ponds. Water in the tailings slurry is siphoned off to evaporation ponds where it evaporates as pure water vapour back into the atmosphere. The remaining dried-out finely powdered solid is held in storage cells. Some of the coarser solid tailings is being used to back-fill stopes (see Land).

An aerial view of the Tailings Retention System at Olympic Dam. The water filled ponds (upper left) are evporation ponds. The reddish brown areas are tailings storage areas.

Waste rock is non-ore bearing rock removed from underground during construction of the main decline, shafts, and tunnels, which provide access for miners to ore-rich areas. Waste rock is hoisted up a shaft to the surface, mixed with dried tailings sand, limestone, fly-ash (a waste product from a coal fired power station at Port Augusta), cement and water to form a material very similar to wet concrete. This mixture is poured from the surface through boreholes into empty underground stopes, and the mined out stopes are filled up.

Not only does this make good use of a variety of waste materials (tailings, waste rock and fly ash), it increases the stability of the underground mine by filling the large empty holes created during mining of the stopes. It also prevents build up of radioactive radon gas in the empty stopes. This is important for the safety of mine employees.

Recycling and reuse

In order to reduce the amount of waste produced, Olympic Dam recycles and reuses as much material as possible. Here are some examples of what is recycled or reused, and how;

• Oil - used oil from machinery is collected, and after treatment is reused as fuel in furnaces in the processing plant.

This worker is stripping the plastic insulation from unwanted copper wire. The copper in the wire is then recovered.

• Paper - paper is shredded and mixed with water to make hydromulch. This is sprayed onto bare disturbed ground at the mine and in Roxby Downs to reduce dust and drifting sand. It holds seeds in place, and following rain plants germinate and bare areas are gradually rehabilitated.
• Timber - waste timber from buildings or other uses is collected, chipped and used as mulch on gardens to reduce evaporation of water. It is also spread on bare ground to reduce dust.

Waste timber from the mine site is collected and stockpiled for later chipping.

• Containers - where possible these are saved and reused.
• 44 gallon drums - these used to be buried after use, but now they are cleaned and reused.

A collection of 44 gallon drums which have been cleaned ready for reusing.

• Tyres from mine vehicles and underground mining machinery - some of these are sold to a company that turns them into rubber linings for vehicles (eg. floor mats, rubber liners for the back of utes, etc). They are also used around the mine site as vehicle barriers and retaining walls.