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RULE 2 - PERMITS <br />h, = head in alluvium <br />• L = length of flow path from the mine to the alluvium <br />The flow rate from the alluvium to the mine workings is calculated below for steady-state <br />conditions. That is, the calculations assume that the cone of depression around the mine workings <br />has grown vertically upward through the overburden to the alluvium and, at the alluvium /bedrock <br />contact, has reached its maximum. This calculation does not account for the time - dependent growth <br />of the cone of depression, but rather considers only the maximum drawdown and therefore predicts <br />the maximum flow rate. The vertical hydraulic conductivity of the overburden between the mine <br />workings and the alluvium is estimated to be 10 ft/d, from data presented by Williams and Clark <br />(1994). The alluvial aquifer area is estimated to be approximately 3.4 x 10 ft2, or 78 acres (three <br />4000 -ft lengths of aquifer averaging 500, 250 and 100 feet wide). The head difference, h, -h,, is <br />estimated at approximately 200 feet, the average distance between the alluvium and the top of the <br />Wadge Coal. The length of the flow path, L, is approximately 200 feet, the vertical distance <br />between the mine workings and the alluvium. Thus, the calculated average inflow is: <br />Q= K.A.(h ,. h,)IL <br />Q = 10 - 5 ft/d - 3.4 x 10 ft - (200 ft) / 200 ft <br />= 34 ft3 /d <br />= 0.0004 cfs <br />= 0.18 gpm <br />• Table 2.05.6(2) -Tl presents a simplified water balance for PSCM based on the assumptions listed <br />above and the resultant calculations performed. The potential depletion to stream flow based on <br />Table 2.05.6(2) -Tl is 4.6 acre -feet per year. <br />PSCM Permit App. 2.05 -67.1 Revision 03/05/10 <br />