Determination of coal mine impacts on surface water bodies (Olifants River)
Ratombo, Avhafuni Percy
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The purpose of the study was to determine the impact of a coal mine on the water quality quaternary catchment B11J. The study area is situated in quaternary catchment B11J of the Olifants Water Management Area. The objectives of the study were to (i) to compare the surface water quality upstream and downstream of the mine in the Olifants River; (ii) to examine the pathways and factors that can contribute to the contamination of the water from the mine flowing into Olifants River. In order to achieve objective (i), surface water was sampled upstream and downstream of the mine, during the summer and winter season in 2015. The pH and electrical conductivity of surface water samples were within SANS 241 specifications. A Piper diagram and durov diagram were also used to analyse the character of the surface water samples. Objective (ii) was achieved by conducting field investigations, specifically of the coal washing plant, stockpile area, mining area (opencast pit) and pollution control dam. The investigation found that contaminated water from the stockpile area, washing plant and open pit is disposed into a lined pollution control dam and re-used for dust suppression on haul roads. Berms and trenches were constructed upstream and downstream of the mine to divert clean storm-water away from the mine. A simplified surface water model was constructed to determine the possible migration of pollution. A groundwater study was conducted to determine the groundwater level and contour lines on site as well as any possible seepage of polluted groundwater into the Olifants River. The results of the particle tracking exercise indicate that the surface flow will drain towards the Elandspruit tributary from the mining area. The flood lines also show that the mine infrastructure is outside of 100 years flood lines. Groundwater levels were found vary from 1.6 mgbl to 51.1 mbgl. The contour lines were indicating that the groundwater flow is heading in a westerly direction from the watershed towards Elandspruit tributary of the Olifants River. It is important for the mine to monitor both ground and surface water upstream and downstream of the mine in order to monitor the contamination trends.