The Study Of The Effectiveness Of Rehabilitation Of Abandoned Dundee-Newcastle Coal Mines On Groundwater And Surface Water Quality

The legacy of mining in South Africa in general and in KwaZulu-Natal (KZN) province in particular, continues to affect the quality of surface water and groundwater resources. Rehabilitation of Northern KZN abandoned coal mines and their discard coal mine dumps had been undertaken by Government in the 1990’s following the emergence of stricter environmental legislation. The purpose of this study was to study the success of the rehabilitation of these abandoned mines in improving the quality of surface water and groundwater resources around the area. Hydrochemical data for the past seven years including data generated during this research was analysed through hydrochemical plots, trend analysis, bivariate and multivariate statistical analyses and calculation of saturation indices using various software, including AqQA, SPSS and PHREEQC. These hydrochemical analyses results were interpreted along with groundwater level and environmental isotope data. The results show that since the start of the monitoring period seven years ago, the groundwater is characterized by circumneutral pH and contains relatively low concentrations of metals. Ionic concentrations of groundwater were assessed and found to correlate with neutralization reactions, specifically calcite and dolomite Acid Mine drainage (AMD) buffering reactions. Time series analysis of saturation indices revealed slight fluctuations for calcite and dolomite, although groundwater appeared to remain oversaturated with respect to these minerals. This was due to the generation of Ca2+, Mg2+ and SO4 2- ions from carbonate- AMD neutralization reactions. Time series data of EC, SO4 2- and total Fe indicated no anomalous values except with few episodes of elevated levels. The main groundwater hydrochemical facies identified was Ca-Na-HCO3. The surface water samples displayed elevated EC at various sampling points, indicative of the impact of both the neutralization reaction and the AMD. The analysis of all available data and information show that the rehabilitation operation has been largely successful, with exception of a few possible seepage zones that have been impacting surface water quality.