PREDICTION TECHNIQUES AND PREVENTATIVE MEASURES RELATING TO THE POST-OPERATIONAL IMPACT OF UNDERGROUND MINES ON THE QUALITY AND QUANTITY OF GROUNDWATER RESOURCES

PREDICTION TECHNIQUES AND PREVENTATIVE MEASURES RELATING TO THE POST-OPERATIONAL IMPACT OF UNDERGROUND MINES ON THE QUALITY AND QUANTITY OF GROUNDWATER RESOURCES
Report No. 699/1/01

EXECUTIVE SUMMARY

1 BACKGROUND INFORMATION AND SCOPE OF INVESTIGATION

Over the past ten years, the issuing of closure certificates has dwindled to a point where very few closure certificates have been issued. Uncertainties in terms of the long-term water quality in these mines are often too great for the Government to issue closure certificates with confidence.

This research was initiated in view of this difficulty in issuing closure certificates. The scope of the investigation was as follows:

To evaluate and document the current impact of closed underground mines on the quality and quantity of groundwater resources, in order to select suitable sites for further detailed investigation, thus generating an impact rating system that could also be applied to operating mines.
To evaluate, with the aid of field observations, various credible preventative options to minimise the undesirable impacts of water quality deterioration and influx relating to underground mining.
To select or design reliable tools for the prediction of water qualities and quantities during the post-closure phase, to provide information for closure and to assess the applicability of these tools to South African conditions.

The first research objective dealt with the evaluation and documentation of the current impact of closed underground mines on the quality and quantity of groundwater resources. This work formed part of the development of a risk assessment procedure. It provided a broad overview of the problems associated with mine water management, identifying the issues that could, in the long run, present serious problems when applying for closure of the mines.

The second objective stated the use of field trials to identify credible management options. Field trials are ongoing at all of the mines through variations in mining methods, monitoring and different solutions that have already been implemented. These solutions may be in terms of water and salt minimisation, impact prediction, alternative water supply for affected parties, desalination and use of mine water. In terms of achieving this aim of the investigation, three existing systems have been investigated. Aspects that should be explored in greater detail have been identified. A selection has been made of issues that will have a positive impact on water quality and quantity.

The third objective related to predictive tools. A wide selection of these tools is generally available. Most of these require expert knowledge of hydrochemical processes and flow dynamics. These tools have been used to model and understand the systems in question. A high priority in this research was the development of alternative and simplified methodologies that can be used as .general tools by the mining community. These simplified methodologies are based on sound principles of flow dynamics, hydrochemistry and geology. They should go a long way in providing a better understanding of the systems investigated.