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<br /> <br />-3- <br />Powderhor Attachment <br /> <br />Calculation of Depletion of Stream/alluvial aquifer system as the result of <br />mining. (Methodology taken from Water, Waste, Land report for CFI.) <br />assumes: No secondary permeability either as a result of natural fracturing <br />or subsidence. <br />Darcy's Law - Q = KA IA <br />where <br />Q = Flow from stream/aquifer system to the mine. <br />KA = Effective Vertical Hydraulic Conductivity , (ft/d) <br />calculated from KA = L L = Total thickness of <br />strata <br />Ll + <br />L1 L2 = Thickness of <br />K1 K2 Lithologic units 1 and. <br />Kl K2 = Vertical hydraulic <br />conductivities of units <br />1 and 2. <br />I = Vertical hydraulic gradient = 1 (dimensionless) <br />A Area of saturated material (f t2) <br />Calculation: L 100 100 <br />KA = L1 + L2 = 37 + 63 -q = 3.7 + 6.3x105 1.6 x 10-g (ft/d.) <br />KI K2 10 1x10 <br />Overburden column is 37~ sandstone and 63a shale. <br />Hydraulic conductivities for sandstone and shale taken from <br />Bureau of Reclamation Tables. (Probably overestimated.) <br />Q=KAIA <br />Q = (1.6x10_q(ft/d)(1)(50'x31,500')= 252 ft3/d = 0.003 cfs <br />31,500 ft of Rapid and Cottonwood Creeks undermined. <br />50 ft saturated width of stream/alluvial system. <br />(Probably overestimated.) <br />ono In the absence of subsidence or flow through natural fractures 9 NO <br />MATERICAL DAMAGE. <br />