Investigating The Potential Impacts Of Bentonite Mining At Matsopa Mine On The Groundwater System

This paper describes the results of geohydrological studies conducted at Matsopa Mine, where a shallow bentonite body is mined, to investigate the potential impacts of mining on the groundwater environment. An understanding of such potential impacts is crucial since the communitiesin the area are dependent solely on groundwater for their domestic water supply.

The studies consisted of a) a hydrocensus to investigate the current groundwater quality and use in the vicinity of the mine, b) geophysical surveys to investigate the presence of geological structures that may influence groundwater migration, c) geochemical investigations of the ore body and host rock to predict the character of potential contaminant impacts, and d) groundwater monitoring to determine whether mining has impacted on the groundwater quality.

The hydrocensus found that the groundwater is used for domestic water supply, as well as livestock watering and irrigation, on a number of farms surrounding the mine. The geophysical surveys conducted with the magnetic and electrical resistivity tomography (ERT) methods revealed the presence of dolerite structures adjacent to and in the vicinity of the opencast pits. These structures are likely to be associated with fractures, joints, fissure and cracks which could form preferential pathways for groundwater migration. The results of geochemical analyses using the XRD and XRF methods showed that both the ore and host rock are dominated by SiO2 and contain very low concentrations of trace elements that could pose a threat to the environment and human health. Groundwater monitoring was done on a bimestrial basis. The groundwater quality was found to be good with little or no evidence of contaminant impacts from mining. Elevated nitrate concentrations at a single monitoring site are likely to be due to agricultural activities on the different farms surrounding the mine. During the time spanned by the monitoring events, increasing water level elevations were recorded in the boreholes surrounding the mine. This observation shows that groundwater recharge to the aquifer system was taking place as a result of the higher rainfall experienced as compared to the preceding years. Activities at Matsopa Mine do therefore not appear to have a significant impact on the groundwater levels in the vicinity of the mine. The results of the geohydrological studies therefore indicate that bentonite mining at Matsopa Mine has not had significant detrimental impacts on the groundwater quality and quantity.

Presenter Name
Lerato
Presenter Surname
Mokitlane
Area
Free State
Conference year
2017