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Using the Theis method for confined aquifers, drawdowns in each aquifer can be estimated • <br />using the following equations. <br />u = Sr= (Equation 1) <br />4Tt <br />0 = 411 TS (Equation 2) <br />W(u) <br />W(u) = 41I Ts (Equation 3) <br />0 <br />r = ( 4Ttu) h (Equation 4) <br />S <br />where: <br />T = Transmissivi ty in ft~/day; <br />0 = Net inflow in ft~/day; <br />s = Drawdown in ft; • <br />W(u) = The well function of u; <br />5 = Storage coefficient (dimensionless); <br />t = Time since discharge began in days; <br />r = Radius to dra wdown in ft. <br />The calculations performed for each aquifer to determine the radius to a one-foot and <br />five-foot drawdown are as follows: <br />Step 1. Solve for "u" using a radius value of one foot and Equation 1. Determine the <br />corresponding value of W(u). <br />Step 2. Solve for 0 using Equation 2. This will be the artificially calculated pumping <br />rate that will permit pit pumpage to occur for a given time period before <br />drawdowns at the highwall exceed the saturated thickness of the aquifer of <br />interest. <br />Step 3. Using the 0 values solved for in Step 2, use Equation 3 but substitute one foot <br />or five feet for the drawdonn(s) and solve for W(u). Determine the <br />corresponding value of u. • <br />Step 4. Solve Equation 5 using the u determined in Step 4 and solve for the radius of <br />influence (r). <br />10 <br />