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Sunnyside Mine-AM ' Water AddWon <br /> DISCUSSION <br /> HYDRAULIC EFFECTS <br /> Based on historical information, the equilibrium water level in re-saturated workings at <br /> the Sunnyside Mine is expected to be near the F-Level (approximately 11,500 Ft <br /> AMSL). Numerical flow modeling of the mine area indicates that, under natural <br /> recharge conditions, it would take approximately 10 years for the water level to reach <br /> 86% of its ultimate recovery and at least another 10 years to reach its final, water-level <br /> condition (Simon Hydro-Search, 1993). At least until the water level has recovered to <br /> the 86% level (i.e., through about Year 10 under natural recharge), it would not be <br /> possible to evaluate the long-term hydraulic effects of flooding the mine on the ground <br /> water and coupled ground-water / surface-water regimes near the Sunnyside Mine. <br /> "Equilibrium" (more appropriately "steady-state")I water level in a ground water <br /> system is determined by Darcy's Law (relating specific discharge to head gradient) and <br /> continuity constraints: distribution of gravitational potential energy, recharge flux, <br /> resistance to flow, and discharge flux. By definition, steady-state conditions are <br /> independent of time: for a given system, the steady-state water-level elevation is <br /> independent of the rate at which water level changes from some transient condition to <br /> the final, steady-state level. That is, potential energy distribution will control the final <br /> water-level elevations for any given long-term regional system: if the system <br /> temporarily has water level above the steady-state elevation, additional discharge will <br /> occur; if the system temporarily has water level elevations below the steady-state <br /> elevation (including due to pumping), recharge will occur. <br /> Artificial flooding of the workings will accelerate the approach to steady-state water <br /> levels from the Current, pumped-down condition, but it cannot change the ultimate <br /> steady-state level. Therefore, supposing that re-establishing natural ground water <br /> conditions is a goal of the reclamation activities, it is beneficial to accelerate the rate of <br /> establishment of steady-state water levels. As a by-product of the process, it will be <br /> possible for all parties to more rapidly evaluate the long-term physical effects of re- <br /> saturation than would be possible under natural conditions. <br /> It is likely that the natural regional water level near the Sunnyside Mine has a seasonal(as well as longer cycle)range <br /> of elevations. However,it is expected that(a)fluctuations are small in comparison to the total vertical thickness of <br /> the system and(b)relative configuration of the natural water table remains the same. Under these conditions,it is <br /> conventional in ground-water hydrology to evaluate a single,steady-state regional flow system(Freeze and Cherry, <br /> 1979,p. 194;Hubbert, 1940;Toth, 1962, 1963) <br /> Geochimica, Inc. 2 ALKALINITY/6-Jun-95 <br />