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Chapter six Groundwater remediatwn 191 - <br /> 1 <br /> 91 -1 The stagnation point, where y is approaching zero, <br /> 2 The sidestream distance at the line of the extraction well, where x = <br /> 0, and <br /> 3 The asymptotic values of y, where x <br /> If these three sets of data are determined, the rough shape of the capture <br /> zone can be depicted At the stagnation point(where y is approaching zero), <br /> the distance between the stagnation point and the pumping well is equal to <br /> Q/270u,which represents the farthest downstream distance that the pump- � <br /> ing well can reach At x = 0, the maximum sndestream distance from the <br /> extraction well is equal to±Q14Bu In other words,the distance between the <br /> dividing streamlines at the line of the well is equal.to Q/2Bu The asymptotic <br /> value of y (where x=—) is equal to±Q/2Bu Thus,the distance between the <br /> streamlines Ear upstream from the pumping well is Q/Bu u <br /> Note that the parameter in Eq VI 13 (Q/Bu) has a dimension of length <br /> To draw the envelope of the capture zone, Eq VI 13 can be rearranged as <br /> 1 =khT4�b <br /> X= ry for positive y values [Eq VI 1 4A] <br /> tan 1+1—J Qu)Yln) <br /> X=- y for negative y values [Eq VX 14B] <br /> tan -�-1—� Qu ly�n <br /> A set of (x, y) values can be obtained from these equations by first <br /> specifying a value of y The envelope is symmetncal about the x-axis , <br /> Example VI 12A Draw the envelope of a capture zone of a " '" <br /> groundwater pumping well <br /> Delineate the capture zone of a groundwater recovery well with the follow- a <br /> mg information <br /> Q = 60 gpm <br /> Hydraulic conductivity = 2000 gpd/ft2 <br /> Groundwater gradient = 0 01 <br /> Aquifer duckness =50 ft <br /> Solution <br /> a Determine the groundwater velocity, u a a <br />