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' GROUND WATER DRAWDOWN TEST CALCULATIONS <br /> 24-HOUR STEP DRAWDOWN TEST <br />' Chase Van Buren <br /> 424 North Van Buren Street, Stockton, California <br />' 8 GALLONS PER MINUTE PUMPING RATE <br />' Assumptions <br /> A constant ground water pumping rate of 8 gallons per nunute test conducted on <br /> 30 May 2001 <br /> • Wells are screened entirely through the upper water table <br /> • Homogenous groundwater aquifer characteristics at observation wells EW-4,MW-3,VW-2, <br /> MW-7, VW-4, VW-1, MW-9 and MW-21A and extraction well EW-3 <br />' The Jacobs Straight Line Method (Distance-Drawdown Method) can be utilized to <br /> calculate hydraulic conductivity, transrnissivity(T) and storativlty yield utilizing draw-down <br /> versus distance on serm-logarithmic paper for each well location (Appendix Z) <br />' Where <br />' K=hydraulic conductivity <br /> T = transrmssivity <br /> S = storativlty <br />' Q = constant ground water pumping rate <br /> As = draw-down per 1-logarzthunc cycle <br /> t= time of pump test <br />' ro = intercept of best fit line with the distance axis <br /> b=thickness of aquifer (sewn penetrated or exposed) <br /> L <br />' Calculations <br /> Q = 8 0 GPM; As =0.50 ft.; t= 1,455 minute; ro = 160 ft. <br />' T = 70Q—As ^# 70(8 0 GPM) —0 50 ft= 1,120 ft /day <br /> 1, <br /> 1,120 ft'/day x 1 gpd/ft -- 0 134 ft'/day= 8,360 gpd/ft <br /> S = T(t) — 640 (ro)2 = (1,120 ft2/day)(1,445 nun) — (640)(160)' = 0.099 <br /> K= T — h= 8,360 gpd/ft — 20 feet=418 ft/day <br /> 418 ft/day(1 cm/sec/2835 ft/day) = 0.147 cm/sec <br /> 1 <br />