Large volumes of freshly broken and crushed sulphide-bearing rock are discarded as waste at metalliferous mine sites. This material commonly gives rise to contamination of surface and groundwater by high concentrations of trace metals and other potentially harmful elements. MINDEC provides a decision-support tool for environmental planners and regulators concerned with the management of mine wastes and with the contamination of waters arising from those wastes. MINDEC has been developed with funding from the UK Department for International Development (DFID) under the KAR (Knowledge and Research) programme, project R7118: 'Cost Effective Evaluation of Hazards from Mine Waste'. It has been developed primarily for use in situations where the resources available for on-site data collection may be insufficient for a full assessment of a large number of sites.
The program can be used: to prioritise mine waste sites for further study/monitoring and/or remediation work on the basis of the threat that these sites pose to ground and surface water quality and to the health of water consumers; to provide guidance concerning the relative risks associated with using different water sources at a receptor site; to predict whether groundwater at the receptor site is likely to deteriorate in quality in the future; to aid in the development of more complete conceptual models of contaminant migration at individual sites; as a predictive tool to provide some indication of water quality at a hypothetical receptor site such as a planned water supply borehole that has not yet been constructed; to carry out human health risk assessments of the water pathway using actual contaminant concentrations at a receptor site where these data are available.
MINDEC considers mine waste contaminant migration in terms of: a source, i.e. the mine waste; a pathway, i.e. a surface waterway or a groundwater body; a receptor, which might be, for example, a surface water body, a water well or a water consumer.
MINDEC provides a 'best estimate' of the threat to ground and surface water quality and to the health of water consumers at a distant receptor site by
calculating: expected concentrations at the receptor site of a suite of potentially harmful trace elements in waters originating from the mine waste site under study; human health risk indices toxic hazard quotients and for arsenic a carcinogenic risk factor) for consumers of the contaminated waters;
a water quality standard (WQS) exceedance index, which provides an indication of the extent to which the expected concentrations at the receptor exceed water quality standards; relative contaminant-element doses (as percentages of the total dose) from surface water, groundwater and other water sources.
The program also gives some indication of: contaminant travel times from the mine waste source to the receptor through the groundwater pathway; the expected duration of contaminant generation at the mine waste site.
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