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Unit 12: Special Features of Audit

Notes
Hydrogeology in the South African Region
Hydrogeology – the study of the interaction of groundwater with surface water bodies,
soil and rock formations and waste rock bodies – forms part of AngloGold Ashanti’s
integrated water management plan as prescribed by South African legislation.
Hydrogeology falls under the Water Management section of the South African
Environmental Management Department. A number of hydrogeology projects have been
undertaken over the past four years. They include isotope analyses to determine the
origin and speciation of water bodies; studies to predict the influx of water into gold
mines within the KOSH (Klerksdorp, Orkney, Stilfontein and Hartebeesfontein) area and
to quantify the future influx of water into the Stilfontein area in the event of mine closure;
and an assessment of the impact of dewatering of mines on neighbouring groundwater
users, both in terms of quantity and water quality.

The main objectives of hydrogeology in the South Africa region are to establish the
following:

 Identification of pollution sources and potential pollution sources (e.g. Tailings
dams, dirty water separation dams, storm water dams);
 Risk assessment and classification of pollution sources;

 Mitigating the paths of pollution sources to prevent their ingress into unpolluted
water;
 Identification of receivers of pollution (e.g. Rivers and other natural water sources)
and mitigation options; and
 Impacts of mine dewatering.
Data obtained from the integrated ground and surface water monitoring network has
enabled the compilation of a number of formal monitoring reports in the South Africa
region. This has allowed for the construction of a detailed groundwater model and predictive
simulations to identify potential groundwater risk. Groundwater contaminant flow
transport models were constructed to quantify possible pollution impacts over a period
of, for example, 20 years. The transport models were ranked according to their salt load
allocation (the higher the salt load, the more polluted the water) and the distance over
which the pollution travels.
From an identification of groundwater risk, AngloGold Ashanti has been able to pinpoint
potential problem areas, and to implement mitigation strategies. These include:

 Responsible management of explosives which contain a high nitrate composition
and therefore the potential to pollute groundwater;

 Implementation of production boreholes to intercept groundwater pollution plumes
and thus reduce the contaminant flow into unpolluted water sources;
 Rehabilitation of soils and continuous monitoring of dam water level overflows to
prevent seepage;
 Maximisation of the re-use of water;
 Installation of under-drains to intercept polluted water in shallow groundwater
tables;
 Regular assessment of evaporation dams, to check salt levels, and of clean water
dams, to prevent the ingress of potential pollution sources;
Contd....

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