M E M O R A N D U M 6 2.3 Water inflows in each zone All major water intersects during development have occurred in Zone 5 as have the large majority of water intersects during diamond hole drilling (Figure 6). Zone 5 is the only high conductive zone with substantial past and present development in the mine. The other high conductive zones are likely to produce similar water flows if intersected. Presently Zone 5 is actively being dewatered, which so far has resulted in significant water pressure drops in this zone. Prior to developing any of the other high conductive zones the potential for high flows and the possible measures of mitigation of such flows should be investigated. Figure 6: Water intersects underground (grey diamond drill hole flow records, red water intersects during development). Left: no zones shown, Right: Zone 5 is shown. 2.3 Water pressure in each zone The water pressure table contains the level water pressures for each zone and each development level. The level pressure is the maximum pressure that was measured in each zone adjusted for the elevation of the development level. Due to the low data density most zones do not allow the creation of reliable water pressure contours, so that the maximum pressure was selected as the most sensible value for a risk matrix. Zone 5 however contains 11 water pressure readings within a small area of high hydraulic conductivity, which allows the creation of water level contours for a section of this zone. If the location of a development area within zone 5 is located in the contoured area the water pressure can alternatively be taken from the water contours rather than from the water pressure table. Presently the only development area that this applies to is the Shaft Access on 1325. The water contours will be updated monthly together with the water pressure table.
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