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.ri .g 190 Practical design calculations for groundwater and sod remedurtion should be strategically located to create a capture zone that encloses the entire contaminant plume If two or more wells are used,the general interest is to find the maximum distance between any two wells such that no con- tamutants can escape through the interval between the wells Once such distances are determined, one can depict the capture zone of these wells from the rest of the aquifer To delineate the capture-zone of a groundwater pumping system m an actual aquifer can be a very complicated task To allow for a theoretical approach, let us consider a homogeneous and isotropic aquifer with a uni- form thickness and assume the groundwater flow is uniform and steady The theoretical treatment of this subject starts from one single well and expands to multiple wells The dLscusszons are mainly based on the work by Javandel and Tsang 2 One groundwater extraction well For easier presentation, let the extraction well be located at the origin of an x-y coordinate system (Figure VI A A) The equation of the dividing stream- Imes that separate the capture zone of this well from the rest of the aquifer (sometimes referred to as the "envelope") Is y=+ Q — Q tan-' y [Eq VI 13] 2Bu 27r,Bu x where B = aquifer thickness (ft or m), Q= groundwater extraction rate (ft3/s or m3/s), and u = regional, groundwater velocity (ft/s or m/s) =Ki Figure VI 1 A illustrates the capture zone of a single pumping well The larger the QJBu value is (Le, larger groundwater extraction rate, slower groundwater velocity, or shallower aquifer thickness),the larger the capture zone Three interesting sets of x and y values of the capture zone Y Stagnation Point Groundwater Flow %K.T X Pumpin Qt2Su Well OJOU !1 -ftiniti lu E a ` Figure W 1A Capture zone of a suigle well F