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Ground Water Drawdown Test Calculations <br /> Former CHASE CHEVROLET Madison Facility <br /> 423 North Madison Street, Stockton, California <br /> Assumptions: <br /> • A constant ground water pumping rate of 6 gallons per minute test conducted on <br /> 24 May 2001. <br /> • Wells are screened entirely through the upper water table. <br /> • Homogenous ground water aquifer characteristics at observation wells EW-2, MW-19A, <br /> MW-20A and MW-21A and extraction well EW-1. <br /> • The Jacobs Straight Line Method (Distance-Drawdown Method) can be utilized to <br /> calculate hydraulic conductivity,transmissivity(T) and storativity yield utilizing draw-down <br /> versus distance on semi-logarithmic paper for each well location (Appendix I). <br /> Where: <br /> K=hydraulic conductivity <br /> T= transmissivity <br /> S = storativity <br /> Q =constant ground water pumping rate. <br /> As =draw-down per 1-logarithmic cycle. <br /> t=time of pump test <br /> 141W ro=intercept of best fit line with the distance axis <br /> b =thickness of aquifer (semi penetrated or exposed) <br /> Calculations: <br /> Q =6.0 GPM; As=0.66 ft.; t=480 minute; r•= 65 ft. <br /> T=70Q-.-As —170(6.0 GPM) -0.66 ft`= 636 ft=/day <br /> 636 ft2/day x 1 gpd/ft=0.134 ftZ/day=4,750 gpd/ft <br /> S =T(t) _ 640 (ro)2=(636 ft2/day)(480 min) _(640)(160)2 = 0.019 <br /> K=T _b= 4,750 gpd/ft=25 feet = 190 ft/day <br /> 190 ft/day(1 cm/sec/2835 ft/day) = 0.067 cm/sec <br />