2009-03-06_REVISION - M1983141 (5)

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Non-Tributary Support: Cash Mine Borehole AdrianBrown r = radius of well [L] The parameters for the evaluation require computation as the mine is a complex well. The specific value ascribed to each parameter is computed below. 2.5.1 Mine Inflow A pumping test of the mine was conducted in August 2006. The test comprised pumping a specific volume of water from the mine via the mine well, and then recording the length of time that the mine water level (measured in the mine well) required to return to the pre-pumping level after the pump was turned off. The results of the test are presented in Table 1. Table 1 - Cash Mine Inflow Test - August 2006 Depth to Water at beginning of test feet 317.85 Volume pumped from mine gallons 6344 Time to recharge to pre-pumping level minutes 4080 Flow rate pm 1.56 2.5.2 Length of Open Interval The length of open interval in this case is the depth of the mine from the original water table. The depth to water in the vicinity (measured at wells approximately 952 feet northwest of the mine well - Plate 2) has been measured to average 30.20 feet in the period 1987-2006. The elevation of the collar of the Cash Mine Shaft is 8050.29 ft4. Thus: Elevation of the groundwater table at the mine = 8050.29 ft - 30.20 ft = 8030.09 ft The depth of the "well" represented by the mine is taken as being equal to the depth of the mine. The lowest level of mine (Level 9) is open to a depth of 668 feet below ground surface (measured from the Cash Shaft collar). Thus: Elevation of the deepest part of the mine = 8050.29 ft - 668 ft = 7382.29 ft The open interval, L, is therefore given by: Open interval of mine (L) = 8030.09 ft - 7382.29 ft = 647.80 ft 2.5.3 Head Loss The head loss resulting from flow to the mine is equal to the average head difference between the "far field" head (taken to be the average head around the mine at a distance sufficient not to be affected by the drawdown due to flow to the mine) and the water level in the mine. For this evaluation, the levels are those taken on August 8, 2006. 4 The Cash Mine Shaft collar elevation is approximately 57 feet lower than the Cash Mine well collar elevation. This is occurs because the Cash Mine Shaft is not vertical, but follows the orebody, which dips approximately north-north east at about 70°. Thus the (vertical) mine well is north-northeast of the mine over its entire length, and is collared up the hill, and at a higher elevation, than the mine shaft. 3 1601A-20070125