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- ~3 - 1 Mining below the upper bench will comprise another factor which may change the stability conditions of the area. As a result of the mining activity, subsidence will occur. Depending on the mining method applied, this subsidence may range between several inches and several feet. Subsidence will certainly influence physical properties of the over- ' burden rocks between the mine elevation and the surface of the upper bench. It will be necessary to evaluate this in- ' fluence once the mining method below the upper bench is known. ' The expected subsidence may have a significant impact on the ground water conditions of the zone between the mine and ' the upper bench. It has to be expected that the subsidence will cause fracturing of the rock and subsequent disturbance ' of any potential aquifers which may exist above the mine. As was discussed in this report, ground water conditions are of ' importance for the stability of the area; we feel that it will be necessary to investigate the ground water conditions in the future and to evaluate their impact on the stability before and after mining. 1 5.4 GROUND WATER CONTROL 1 The importance of ground water conditions below the upper ' bench is evident from the results of our study. If, during further studies, ground water is found above the mine, de- ' watering may be required to increase the overall stability. As discussed earlier, dewatering may be brought about simply by ' the subsidence of the area and by fracturing of the rocks above the mine. It is also possible that dewatering will be achieved simply by driving of the mine tunnels. If, for ~ohatever reasons, dewatering is not achieved, additional drainage measures may have to be undertaken to eliminate any potential aquifers above ' cEO~wRO ca+suinrw, iHC.