Surface Mining

Author: Alan Cluett ~ Environmental Consultant, Holcim South Africa

( Article Type: Explanation )

Mining, by its very nature, is not sustainable into the future. Through the process of mining, finite natural resources, in the form of minerals, are extracted from the Earth’s crust, beneficiated and consumed by our society. We see evidence of mining activity throughout South Africa, with historic evidence of mining going back to before the Iron Age. In fact, Stone Age people were gathering selected rock types from small ‘surface mines’ to make their stone implements.

The impact of poor past mining practice and the lack of mine rehabilitation on closure is still being felt by the current generations. The Department of Mineral and Energy estimates that there are as many as 8000 unrehabilitated or abandoned mines that still require some form of environmental attention in South Africa.

Our society is more dependent on mines today than ever before. Consider the items we all use on a daily basis:

• bricks, mortar and concrete in our homes, classrooms, hospitals, roads, dams, canals, churches and shops;
• copper, iron or aluminium used in our water pipes, electricity and telephone cables;
• steel and zinc used for our roofing materials;
• cars, televisions, computers, stoves, cooking pots, screws, nails, fences, jewellery, glass, inorganic fertiliser…

We create the demand for the minerals and are dependent on mines to support our desired lfestyle. Broadly speaking, there are two types of mines – underground and surface. Considering the latter, surface mining includes:

• Large-scale opencast mines that are kilometres long and wide, and more than 300 metres deep. Mines such as these supply manganese, iron ore, chrome, diamonds, platinum and coal;
• Medium to small quarries that supply building aggregate;
• Small-scale artisinal mines employing a handful of people who supply a range of minerals, including diamonds, gold, coal, gem stones, potting and brick clay.

Surface mines offer advantages and disadvantages when compared to underground mining. Amongst the advantages are that it is cheaper, can recover more of the resource (usually up to 100% within the mining excavation), is safer and can use larger-scale mining equipment offering higher production rates. Disadvantages include its high visibility, the large-scale surface disturbance and the limited economic depth to which mining can take place.

Environmentally responsible miners are always looking at new ways to minimise the impacts of their operations on the environment. Some of these include:

• Keeping the mining ‘footprint’ (the disturbed area) to a minimum;
• Ensuring the maximum extraction of the mineral from the smallest area;
• Minimising the risks of surface and groundwater pollution;
• Minimising the consumption of energy in the form of diesel, petrol and electricity used in mining and processing operations;
• Minimising emissions to atmosphere in the form of particulate (dust), exhaust fumes from vehicles and smoke stacks;
• Increasing employee training, including environmental, safety and health awareness;
• Investing in the local community infrastructure; and
• Through both concurrent and post-closure rehabilitation, returning the mining areas to positively useful and selfsustaining landforms.

On closure of surface mines, they can be rehabilitated to many useful landforms, including:

• Water storage areas and associated recreational facilities;
• Creation of botanical gardens and adventure centres;
• Housing of vehicle test centres;
• Establishment of office parks and shopping complexes;
• Agriculture – crops and grazing; and,
• Land filling with selected wastes.

As consumers of the minerals, we have a responsibility to:

• Ensure that we support environmentally and socially responsible miners;
• Recognise our own responsibility for creating the demand for mined materials (the mines would not be there if we did not demand the minerals and products) and accordingly plan for our future developments and lifestyles to consume the minimum possible resources.