The management of recharge and quality of the underground water in the Klerksdorp area with specific reference to post closure at the Stilfontein Gold Mine (1952-2000) by ANET SPANGENBERG MINI DISSERTATION Submitted in partial fulfillment of the requirements for the degree MASTER OF SCIENCE in GEOGRAPHY AND ENVIRONMENTAL MANAGEMENT in the FACULTY OF SCIENCE at the RAND AFRIKAANS UNIVERSITY STUDY LEADER: DR. J.F. DURAND ASSISTANT STUDY LEADER: DR. J.M. MEEUWIS OCTOBER 2000 Contents: Page List of tables 4 List of figures 5 Acknowledgements 6 Abstract 7 Introduction 8 Problem Statement 11 Study area 13 3.1 Geology 13 3.2 Dykes and Sills 15 3.3 Regional climate 15 3.4 Land use 15 3.5 Natural vegetation 17 3.6 Surface water 18 3.7 Groundwater 19 3.7.1 Depth of water table 26 3.7.2 Presence of boreholes 28 3.7.3 Geohydrology of the Dolomites 29 3.7.4 Possible impacts of mining on the groundwater 30 3.8 Interaction of surface water and groundwater 31 3.9 Groundwater recharge 34 3.10 The gold mining industry 37 3.10.1 Stilfontein mine water balance 38 3.10.2 Interaction of mine water with groundwater 39 3 Contents continued Page Literature review 41 Data collection and methodology 43 Discussion of results 44 6.1 Recharge of aquifers 44 6.1.1 Rainfall 44 6.1.2 Rainfall vs. Pumping 45 6.2 Aquifer Recharge 52 6.3 Water Quality 52 Conclusions 58 Recommendations 59 References 60 4 I. List of tables Page Table 1: Groundwater abstraction by mines 2 1 Table 2: Contaminants, sources and areas affected 3:3 Table 3: Rainfall: After Rosewarne vs. Composite of the rainfall 46 Table 4: Annual Rainfall; "Shallow" "Deep" Water Levels 47 Table 5: Pumping ex-Stilfontein Mine 50 Table 6: Groundwater flow in the Stilfontein Gold Mine 52 Table 7: Modified hydrologic balance after Enslin (1971) 54 Table 8: Margaret Shaft water quality: 1997-2000 55 5 IL List of figures Page Figure 1: The study area: Klerksdorp, Stilfontein and Hartebeestfontein 10 Figure 2: Site map of Stilfontein Gold Mining Company 14 Figure 3: General geology of the study area 16 Figure 4: Surface water features of the Stilfontein Mine 20 Figure 5: Stilfontein Rainfall: modified Rosewarne (1982) 22 Figure 6: Stilfontein Gold Mine: Volumes Pumped 23 Figure 7: Stilfontein Gold Mine: Monthly Pumping vs Annual Rainfall 24 Figure 8: The various elements of recharge and interrelationships 35 Figure 9: Stilfontein Mine Water Balance 39 Figure 10: Hartebeestfontein Gold Mine: Rainfall vs. Deep Water Table 48 Figure 11: Hartebeestfontein Gold Mine: Rainfall vs. Shallow Water Table 49 Figure 12: Stilfontein Gold Mine: Annual Pumping vs Annual Rainfall 51 Figure 13: Flow of groundwater 53 Figure 14: Margaret Shaft Water Quality: Time Series 56 Figure 15: Koekemoer Spruit: EC vs Sulphate Time Series 57 6 III. Acknowledgements I would like to express my thanks:- To the Stilfontein Gold Mine Management & Staff for all the information made available to me and for their hospitality during site visits; To Dr. Stoch for his knowledge and patience; To my study leaders Dr. Durand and Dr. Meeuwis for their attention to detail, research experience, guidance and advice. I would also like to thank my long suffering parents and Malcolm for all their love and support, without which this thesis would never have seen the light of day. Any merit in this treatise is due to Divine guidance, the errors are my own. 7 IV. Abstract Mining has taken place in the Klerksdorp area since gold was discovered in 1887 and the conglomerates were mined in the Town lands. The mining history of Stilfontein goes back to 1888 when the Strathmore Reef was discovered and worked. During the early period no attention was paid to the impact of mining on the environment. Since the 1992 Rio Conference the focus has shifted to sustainable development and environmental well-being. This study investigates the present surface and ground water situations at Stilfontein Mine with the view to making informed management decisions for the pre- and post- closure periods. Recommendations are based on the observations and discussions. Samevatting Sedert 1887 vind mynbedrywighede in the Klerksdorp omgewing plaas waar konglomerate op die Town lands gemyn is. Die geskiedenis van Stilfontein strek van 1888 toe die Strathmore rif ondek en gemyn is. Uit die staanspoor is daar Been aandag geskenk op die aanslag van die mynbedrywighede op die omgewing nie. Sedert die 1992 Rio Konferensie het die klem verskuif na volhoubare ontwikkeling en omgewingsgesondheid. Die studie ondersoek die huidige oppervlak en groundwater toestand van die Stilfontein Myn met die ingeligte besluitneming as doel ten opsigte van die voor- en namynsluiting..speriodes. Aanbevelings is op die waarnemings en bespreekings gegrond. 8 1. Introduction There are four major gold mines active in the Klerksdorp area, namely Stilfontein, Hartebeestfontein, Buffelsfontein and Vaal Reefs (KMMA, 1997). Many changes to the mine business structures have taken place over the years. To ensure the safety of the underground mine workers, some mines had to dewater the overlying aquifers. This study will focus on the Stilfontein Mine, as it was and is still the mine responsible for the major extraction of ground water in the area (Figure 1). The other mines do not pump significant volumes of ground water, as owing to the nature of the geology, they are relatively dry when compared to Stilfontein (Rosewarne, 1982). During January 1992, Stilfontein Gold Mine ceased underground production owing to the decline in the economy and gold market. Underground mine closure meant that Margaret Shaft could stop pumping the ground water, but was obliged to continue in accordance with an agreement with Hartebeestfontein Gold Mine. It was estimated that if Stilfontein were to cease pumping, the mine void would fill with water within three months. The danger, however, exists that water from Stilfontein Mine, will flood the workings of the neighbouring mines. Hartebeestfontein Mine does not have the pumping capacity and necessary equipment as the need never arose to handle large volumes of water (Hodgson, 1990). As Stilfontein Mine is situated upstream from the other mines in the area in respect of the hydraulic gradient, water entering Stilfontein will eventually flow into Hartebeestfontein Mine then to the Buffelsfontein Mine and finally flood the Vaal Reefs Mine. This is due to the fact that the areas between the mine rock pillars, which were rich in gold ore, had been mined out. As a result, there are underground connections between the mines. Underground connections are also maintained between mines, which serve as escape routes during emergencies. 9 Due to the North/South dip in the ore body, Vaal Reefs Mine is currently mining at levels 'deeper than the neighbouring mines. If Vaal Reefs were to pump substantial volumes of ground water, the capital and running costs would be high, as additional pumping equipment would have to be installed at great depths. The Klerksdorp mines have addressed the concerns about the water situation. The need for cooperation is dealt with by a "Water Forum", for without this cooperation it would not be possible to implement an integrated water management policy. In the Stilfontein area, various dolomitic aquifers are utilized by farmers, homeowners, informal settlements and industries. Because of the demand on freshwater more focus is now placed on the sustainability of the ground water resources. Stilfontein Mine has dewatered a valuable resource and the water currently being pumped can be utilized more efficiently (DWAF, 200). The aquifer in the Koekemoer Spruit area, a sub-catchment of the Vaal River, is impacted on by a number of active and abandoned mines. Past, present and the anticipated future impacts of mining needs to be identified to manage and mitigate the negative and amplify the positive impacts. It is advisable that management decisions be taken by well-informed managers, using adequate information based on accurate data. Legend: CI Dams /V Rivers A/ National Routes A Other Routes Frit Towns MINE WASTE SOLUTIONS Source: I ENVIROGREEN Figurel: The study area of Klerksdorp, Orkney, Stilfontein and Hartebeestfontein Scale: 10000 0 10000 20000 Meters 2. Problem Statement While in operation, it was necessary for Stilfontein Mine to pump water to the surface to prevent the mine from flooding and to ensure the safety of the underground workers. Currently only Margaret Shaft is pumping water to prevent Hartebeestfontein Mine from flooding. Hartebeestfontein Mine carries the cost of both the pumping of water and the maintenance of the pumps. The problems which may arise from dewatering dolomitic compartments, are, inter alia, water pollution, the formation of dewatering cones (the localized lowering of water tables) and the potential for accelerated sinkhole formation. All these phenomena can influence the drainage patterns of the river catchments involved. This study, will focus on: the recharge of the aquifers; the impact the discharge water on the Koekemoer Spruit area; the quality of the ground water pumped to the surface as well as the water discharged into the Koekemoer Spruit and determining. the suitability of water for alternative use. By quantifying the recharge, the mine will be able to establish the volume of water that it will have to pump from underground after the recharge via the Koekemoer Spruit is eliminated and seepage from tailings dams, no longer in use, has declined, or ceased. Recharge by rainfall [EU] may, however, continue to be a problem. If this recharge can be intercepted and prevented from entering the Stilfontein Mine, the water pollution will be reduced, as contact with the stope surface and mine water rich in sulphates which have an acid forming capacity, will be avoided.