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where <br />' Q = well pumping rate, 0 00019 m3/sec <br /> T = transmissivlty, 0 00022 m2 <br /> /sec <br /> t = pumping time, 3 15x 10' sec (1 year) <br /> r = well diameter,0.15 m <br /> S = specific yield,0.08 <br /> d = distance between wells, 20 m <br />' s = 19 m (6.2 feet) <br />' The actual drawdown in the wells will be more than 6 2 feet due to decreased transmissivity <br /> when the thickness of the aquifer decreases, when the water table drops Additional drops in the <br /> hydraulic head may be affected by water flow through the screen and sand pack, by borehole <br />' skin developed during drilling and screen clogging by fine particles, or by precipitating minerals <br /> i <br /> Additional drop of the head in the aquifer due to a decrease in thickness can be calculated from <br />' the following equation <br /> s' = s - (s2/2b) (Driscoll 1986) <br /> 1 where <br /> s' = theoretical drawdown, 6 feet <br /> s = measured drawdown in the well <br /> b = aquifer thickness when no pumping is taking place, 20 feet (from the well log) <br />' s = 7 67 feet (2 34 m) <br />' Such drawdown will occur in the area of the middle well, RW3 Drawdowns in the other wells <br /> will be less because each of them ;s influenced by only one well Additional drawdown, caused <br /> by factors dependent on well construction, will only occur inside the well casing; it can be calcu- <br /> lated using the following equation <br /> eh= 0 Ola(Qs/kF)°S <br />' where <br />' a = coefficient(6-8 for perforated screens) <br /> Q = well pumping rate, 16 m3/day <br /> k = hydraulic conductivity, 3 04 m/day for 6 1 m (20 feet)-thick saturated zone <br /> F = active surface of the screen at RW3, 0 2 m2 <br />' s = drawdown in the well, 2 34 in <br /> Ah= 0 47-0 63 m (1.54-2 06 feet) <br /> Total drawdown expected in well RW3 is 9.21-9.73 feet (2 8-3 0 m) <br /> o6O/-W"42rju19Ift 8 <br />