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RULE 2 - PERMITS <br />• T = transmissivity <br />I = hydraulic gradient <br />W = width of aquifer for which the flow is calculated <br />For the bedrock units, the average hydraulic gradient for the northern half of the permit <br />area is approximately 200 feet in 1.25 miles, or 0.03. The width of the aquifers <br />perpendicular to the flow direction in that area is approximately 2.5 miles, or 13,200 feet. <br />The sum (transmissivity is an additive property; Freeze and Cherry, 1979) of the range of <br />transmissivities for the overburden, Wadge Coal, and underburden is 0.049 to 5.3 ft /d. <br />Substituting these values into the equation gives: <br />Q =T•I•W <br />= (0.049 to 5.3 ft'/d) - (0.03) - (13,200 ft) <br />= 19.4 to 2,098 ft ; /d <br />= 0.1 to 10.9 gallon per minute <br />= 0.16 to 17.6 acre -feet per year <br />The calculated flow rate relies on the transmissivity values based on the saturated <br />thicknesses of the aquifers actually intersected by the monitoring wells, which were from <br />37 to 42 feet for the overburden, 7 to 10 feet for the Wadge coal, and 67 to 74 feet for the <br />underburden. As the saturated thicknesses of the overburden and underburden could vary <br />across the permit area, the flow rate calculated above should be considered an estimate. <br />The macroscopic groundwater flow velocity can be calculated through the bedrock <br />aquifers can be calculated using the equation (Freeze and Cherry, 1979): <br />V =K-I /9 <br />PSCM Permit App. 2.04 -50 Revision 03/05/10 <br />