Laserfiche WebLink
inclilde.the inflow from underlying aquifers through fault z~mes. The model <br />c.utput has been augmented wih a separate analysis of ground water discharge to <br />Y.he mine from the fault zones. <br />The ..inflow at the fault crossings was calculated using ttie line-sink, <br />constant-drawdown equation (Lohman, 1972). A time-dependent analysis was <br />performed for three of ten anticipated major fault crossings which are <br />expected to yield inflows to the underground mine. These faults are referred <br />to as fault numbers 4, 8 and 9. Locations of the anticipated fault crossings <br />are shovm on Nap 23, Mine Plan. The controlling parameters were the transmis- <br />sivity and storativity of the source aquifer (Trout Creek Sandstone), the <br />length of .the line sink (fault crossing), the difference in elevation between <br />the piezometric surface and the base of the mine zone, and the time in days <br />since .the discharge began. The analysis was carried out over ten years, until <br />steady-state conditions prevail. Two important assumptions make the analysis <br />conservative: (1) the hydraulic conductivity of each fault zone is infinite; <br />and (?_) the radius of influence from depressurization of the underlying <br />aquifer does not cause drawdown in adjacent fault zones. Therefore, the I. <br />inflow rates calculated are the maximum average annual rates anticipated. <br />.Input for discharge calculations for fault crossings are shown on Table B, <br />.Line-Sink Analyses Input. Results of discharge calculations for fault <br />crossings are shown on Table C, Predicted Inflows for Foidel Creek Mine. <br />As shown, the pattern of mine inflow is dependent: on the rate of mining <br />advancement, and particularly the timing of anticipated fault crossings. The <br />total inflow calculated represents the average rate of discharge to the mine <br />over each year of mining. Initial inflow rates at any fault crossing at the <br />time the fault is intercepted could be much higher than average calculated <br />inflow for the first years of fault interception. However, drawdown of the <br />piezometric surface in the vicinity of each fault crossing will cause inflow <br />rates to decline rapidly over the course~of several days. Weighted average <br />discharge rates for each year of mining were calculated for mass-balance <br />analyses of aquifer depletion and salt loading. <br />The calculated inflow from all sources was accumulated to determine . <br />total ground water inflow to the underground mine. Units of discharge were ~ <br />Ex. 33-2 <br />Revised 7/7/86 <br />