Water is vital to the Northparkes mining and processing operations. Some water used in the mine is rainwater, collected from the roof surfaces of various buildings on the mine site. This is called stormwater. However, because of the low rainfall and high evaporation in the district, rain alone cannot supply enough water. The local creeks (the Bogan River and the Goonumbla Creek) only flow occasionally, and cannot provide enough water either. Therefore, most of the mine's water comes via a pipeline from a ground-water aquifer known as the Lachlan Alluvials, near the Lachlan River, in Forbes. The town of Parkes also gets its water from this source. The mining company purchases this ground water from the local council.
Great care is taken at Northparkes to recycle as much water as possible, both to save the costs of purchasing extra water, and for environmental reasons.
Another important aspect of water management involves control of contaminated water. The company has a responsibility to ensure that contaminants from the tailings dam, from the processing plant or from other sources do not enter the water table (polluting the ground water), or the local creeks. This is important as the mine lies in the Murray-Darling catchment, a huge basin which extends over most of NSW and the ACT, and into Queensland, South Australia and Victoria. Some creek water from the mine district ultimately ends up in the Murray River. The Murray-Darling catchment contains much of Australia's agricultural activity and is already under severe stress because of the effects of salination and other pollution. Careful management of contaminated water at Northparkes can help prevent further damage to Australia's most important river system.
Read on to find out more about how water at Northparkes is used, controlled, treated and recycled.
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Water supplied from the Lachlan Alluvials is used in the ore processing plant for flotation. This process separates the valuable chalcopyrite ore mineral from unwanted rock material. After flotation, the water contains about 55% powdered rock and flotation chemicals. It looks like mud and is called tailings. |
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The tailings is pumped through thick plastic pipes from the ore processing mill to the tailings dams. |
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In the tailings dams, some water evaporates as pure water vapour, back into the atmosphere, leaving the dry powdery waste slurry material, and flotation chemicals behind in the dam. |
Other water is reclaimed from the tailings dam after the solid tailings have settled to the bottom, leaving clear water behind. This water is pumped back to the process water dam, and recycled through the ore processing plant. This photo shows the process water dam in the foreground, with the ore processing plant behind.
The flotation process plant is constructed on a concrete apron that collects any spillage and returns it to the processed water dam, rather than allowing it to soak into the ground.
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Do you ever help wash your family's car? What do you think happens to the dirty foamy water that you rinse off your car? |
Wash-down water comes from outside the mine and is used for washing vehicles and machinery. After use it contains mud and clay, grease, oil and detergents. Therefore, vehicle and machinery washing at Northparkes is done on concreted areas which have walls around them to prevent spillage from spreading and soaking into the ground. Drains allow the dirty water to flow into settling ponds where the mud settles to the bottom. The clear water is then pumped to the process water dam, and recycled through the processing plant. |
Potable water is water for domestic use in kitchens, bathrooms and toilets. Water required for potable use is stored in a separate tank for use across the site. After use it is contaminated with soaps, detergents and sewerage. It is pumped to a sewerage plant constructed on the mine site, where it is treated and pumped back to the process water dam. From here it is used in the processing plant. Refer to arrows numbered 6 on the water flow chart.
