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)GY GROUNDWATER AND WELL HYDRAULICS 155 <br /> TABLE 4.4 Relation of Well Loss Coefficient <br /> to Well Condition (after Walton'O) <br /> Well Loss Coefficient <br /> C, mini/ms Well Condition <br /> 0.5 Properly designed and developed <br /> 0.5 to 1.0 Mild deterioration or clogging <br /> 1.0 to 4.0 Severe deterioration or clogging <br /> >4.0 Difficult to restore well to <br /> original capacity <br /> s <br /> bilizes.34,90,59 The discharge is then increased through a successive <br /> series of steps as shown by the time-drawdown data in Fig. 4.31x. <br /> Incremental drawdowns As for each step are determined from ap- <br /> proximately equal time intervals. The individual drawdown curves <br /> should be extrapolated with a slope proportional to the discharge o- <br /> in order to measure the incremental drawdowns. § <br /> From Eq. 4.67 and letting n = 2, <br /> Q = B + CQ (4.68) <br /> Therefore, by plotting s�/Q versus CQ (see Fig. 4.31b) and fitting a 1 <br /> straight line through the points, the well loss coefficient C is given <br /> by the slope of the line and the formation loss coefficient B by the <br /> is intercept Q = 0. i <br /> at. Rorabaugh55 presented a modification of this graphic analysis to <br /> ce determine n in cases where it deviates significantly from 2. <br />,ss <br /> ur Specific Capacity <br /> of If discharge is divided by drawdown in a pumping well,the specific <br /> by capacity of the well is obtained. This is a measure of the produc- ' <br /> ee tivity of a well, clearly, the Iarger the specific capacity, the better <br /> on the well. Starting from the approximate nonequilibrium equation ) <br /> (Eq. 4.41) and including the well loss, <br /> old � x <br /> 3 <br /> C _ 2.30Q 2.25Tt l <br /> Ile s,� 417 <br /> T log r 2S + CQn (4.69) <br /> 1 <br /> so that the specific capacity <br /> vn <br /> 4 s <br /> Ily Q __ 1 <br /> ta- s� (2.30/47rT)1og(2.25Tt/r�2S) + CQ" {4.70) <br /> -' <br />