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Schwartzwalder Mine -Hydrologic Evaluation of Mine Closure and Reclamation 39 <br />5. The rate of rise of the mine pool decreases as the elevation of the mine pool increases. The RZ <br />correlation between rate at which the water level in the mine is rising and elevation has a negative <br />slope and is 0.4672. <br />6. The rate of inflow decreases as the elevation of the mine pool increases. The Rz correlation <br />between inflow and the elevation of the mine pool has a negative slope and is 0.5425. <br />5.2.4 Projected Final Water Level <br />Although pre-mining static water levels were not measured prior to development of the Schwartwalder <br />deposit in the 1950's, the expected level to which water will rise in the flooded mine can be calculated <br />based on the observed inflow rates over time. <br />Two known conditions are used in the calculation: (1) dewatering mine inflow when the Schwartzwalder <br />was advanced to its furthest depth (with pegmatite drillholes plugged) and (2) pumping rates during the <br />pilot plant test in July and August, 2007 (with the pump set at 27 ft below the collar of the #2 shaft in the <br />Steve Level. In both cases, the flow was accurately measured, and the pumping water level is known. The <br />static water level is not known, and can be calculated iteratively using the Theim steady-state equation for <br />Theim equation for steady-state radial flow to a well: <br /> _ 2~rLKH <br />Q <br /> 1n~R/rn) <br />where: Q = Volumetric inflow to the mine [L3T'] <br />L = Length of the well screen [L] <br />K = Hydraulic conductivity [LT''] <br />H = Drawdown [L] <br />R = Radius of influence [L] <br />rh = Radius of the well bore or mine workings [L] <br />Re-arranging to solve for hydraulic conductivity (K): <br /> Q ln(R/rh) <br /> K _ <br /> 2~rLH <br />Or to solve for drawdown: <br /> Q 1n~R/rti) <br /> H _ <br /> 2~rKL <br />The iterative calculation involves first solving the Theim equation for the hydraulic conductivity that would <br />produce the 180.1 gpm observed average inflow from bedrock when the mine was fully excavated10. Next, <br />a second Theim equation is solved for drawdown that would produce the 1.2 gpm observed during the pilot <br />plant pumping test, with the pump set at 27 ft below the Steve Level shaft opening. The equation is set up <br />to allow any drawdown up to a maximum of 342 ft (the height of the hillside directly above the #2 shaft on <br />the Steve Level, plus the depth of the pump below the collar). The calculated drawdown is then used to <br />determine the saturated thickness (L) in both equations. The two equations are solved iteratively for K, H, <br />and L. <br />10 Average inflow at full depth was 188.9 gpm after the pegmatite coreholes were plugged and the initial storage deficit was met. <br />Given 8.8 gpm average infiltration from surface, the yield from bedrock was approximately 180.1 gpm. <br />4109B.071116 Whetstone Associates <br />