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A pumping test has been completed in a confined aquifer. The aquifer is composed of clean fine sand and is overlain and underlain by silty clay units of very low permeability. Drilling indicates that the aquifer averages 40 m thick in the vicinity of the pumped wells. During the test the hydraulic head of the confined aquifer remained above the base of the overlying silty clay unit. A fully penetrating well was pumped at a rate of 1200 mº/day. Drawdowns were measured in three fully penetrating observation wells located 40 m to the east, 90 m to the east and 190 m to the north of the pumped well. A record of the drawdown versus time measurements for the three Wells is presented in the table below. Use the Cooper Jacob method with time-drawdown data at observation well #1 to calculate transmissivity (m-/day) and storage coefficient (Hint: Use the semi-log graph provided to work on time-drawdown data.) Table: Drawdown data from the aquifer Obs. 3 r 190 m) Time (min) since start of pumping 2.40 3.45 4.55 6.32 8.19 10.16 12.20 17.99 25.76 36.62 50.00 71.97 93.30 115.66 144.58 202.32 273.74 375.26 516.10 728.93 938.45 1158.05 1440.00 0.05 0.15 0.28 Drawdown meters) Obs. #1 Obs. #2 Ir 40 m Ir = 90 m 0.24 0.48 0.75 1.15 1.53 0.03 1.88 0.06 2.20 0.10 2.93 0.26 3.66 0.52 4.42 0.89 5.11 1.30 5.94 1.87 6.54 2.33 7.04 2.73 7.56 3.17 8.36 3.87 9.07 4.52 9.82 5.22 10.58 5.93 11.39 6.71 11.98 7.28 12.47 7.76 12.98 8.25 0.43 0.62 1.00 1.42 1.92 2.49 3.15 3.66 4.09 4.55
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