The effect of Grootvlei mine water on the Blesbokspruit

M.Sc.Gold mining activities are widespread in the Witwatersrand area of South Africa. These have significant influences, both positive and negative, on the socio-economic and bio-physical environments. In the case of South Africa’s river systems and riparian zones, mining and its associated activities have negatively impacted upon these systems. The Blesbokspruit Catchment Area and Grootvlei Mines Limited (hereafter called “Grootvlei”) are located in Gauteng Province of South Africa. The chosen study area is east of the town of Springs in the Ekurhuleni Metropolitan Municipality on the East Rand of Gauteng Province. Grootvlei, which has been operating underground mining activities since 1934, is one of the last operational mines in this area. Grootvlei pumps extraneous water from its underground mine workings into the Blesbokspruit, which includes the Blesbokspruit Ramsar site. This pumping ensures that the mine workings are not flooded, which would result in the gold reserves becoming inaccessible and would shortly lead to the closure of Grootvlei. This closure would further affect at least three other marginal gold mines in the area, namely, Springs-Dagga, Droogebult-Wits and Nigel Gold Mine, all which rely on Grootvlei’s pumping to keep their workings dry. Being shallower than Grootvlei, they are currently able to operate without themselves having to pump any extraneous water from their underground workings. A cessation of pumping would also cause flooding of the lower workings of the neighbouring Consolidated Modderfontein Mine. If pumping does not take place the water will eventually percolate to the surface, initially in the Nigel area and eventually throughout the entir e Far East Rand, which would lead to substantial economic losses. This study was undertaken to establish whether Grootvlei’s pumping activities of extraneous water from underground mine workings into the Blesbokspruit has had, and is still having, an impact on the water quality of the Blesbokspruit and, if so, how this impact can be minimized or eliminated. Water quality of the Blesbokspruit was analysed and trends in four selected variables, i.e. pH, Electric Conductivity, magnesium and sulphate content, are discussed in this report. These variables were analysed in relation to three categories, namely the sample point position, seasonal influences and four periods of pumping operations. The sample position immediately downstream of the discharge point of Grootvlei, where the extraneous water from their underground mine workings is pumped into the Blesbokspruit, as well as the samples collected in the dry seasons, recorded the poorest overall water quality values in The Impact of Grootvlei Mine on the Water Quality of the Blesbokspruit ii all four variables. Although the sample position and seasonal changes influenced the water quality of the Blesbokspruit, it was found that the periods of pumping had the most significant influence on the water quality, with a decrease in water quality after the huge increase in pumping volumes, which commenced in October 1995. It was also established that the Blesbokspruit wetland does not have the capacity to purify the water in the Blesbokspruit in order to maintain similar water quality conditions found upstream from the mine. This could be due to the wetland already having too many contaminants in it. The analysis concludes that the pumping of extraneous water from underground mine workings into the Blesbokspruit has had and is still having, although to a lesser degree, a major influence on the deterioration of water quality of the Blesbokspruit. The strategic management plan of Grootvlei, as well as the feasibility study to establish the best -suited scenario for reducing water ingress into the underground mine workings were discussed. In addition, the following recommendations were made in order to assist Grootvlei in improving the water quality of the Blesbokspruit: Strict compliance with environmental law regarding the requirements set out in the water extraction licence of Grootvlei. Grootvlei should adhere to its statements and undertakings to improve the water quality pumped into the Blesbokspruit. Grootvlei should expand on its increased environmental awareness by ensuring that communication channels are open between Grootvlei and the community. This is essential to ensure that Grootvlei is made aware of issues and concerns of the community and that the community is aware that their issues and concerns have been heard, understood and acted upon by Grootvlei. Grootvlei should become actively involved in the activities and decisions of the Blesbokspruit Catchment Forum, and should be a permanent member thereof. The use of Phytoremediation, trees and riparian zones could be implemented as an alternative to, or in conjunction with current practices to improve the water quality of the water before it is pumped into the Blesbokspruit by Grootvlei. Phytoremediation can also be used in order to reduce the amount of water ingress into underground workings, by establishing vegetation, such as trees, to absorb and evapotranspirate water at areas where ingress occurs. Procedures in the reduction of the surface water ingress to the underground mine workings should also be implemented. Monitoring the water quality pumped into the Blesbokspruit, as well as monitoring the amount of water ingress into the underground mine workings must be continued. A study for the restoration of the Blesbokspruit wetland needs to be implemented urgently