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Ground Water Drawdown Test Calculations <br /> West Clay Properties <br /> I639 West Clay Street, Stockton, California <br /> Assumptions <br /> • An 8-hour step draw-down ground water pumping test was conducted on 19 July 2001 <br /> Pumping rates of 4, 5 and 6 gallons per minute (GPM)were utilized for the test <br /> I0 Extraction well and observation wells were screened in deep water zone <br /> • Homogenous ground water aquifer charactenstics at observation wells MW-1, MW-2 and <br />' MW-3 and extraction well EW-2 <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-loganthmic paper for each well location(Appendix F) <br />' Where <br />' K=hydraulic conductivity <br /> T=transmissivity <br /> S =storativity <br /> t• Q =constant ground water pumping rate <br /> As =draw-down per 1-logarithmic cycle <br /> t=time of pump test <br /> r.=intercept of best fit line with the distance axis <br /> b =thickness of aquifer(semi penetrated or exposed) <br />' Calculations <br /> 4 GPM <br />' • As= 1.2 ft.; t= 120 minute; r ft. <br /> Q = 4.0 GPM, � o= 80 <br />' T = 70Q—Os -+ 70(4 0 GPM)— 1 2 ft =230 ft2/day <br />- 230 fl/day x 1 gpd/ft— 0 134 ft/day= 1,740 gpd/ft <br /> S = T(t) —640 (ro)2 = (230 ft2/day)(120 min) — (640)(8 0)2 = 0.007 <br /> K= T —b = 1,740 gpd/ft—20 feet= 87 ft/day <br /> 87 ft/day(1 cm/sec/2835 ft/day) = 0.031 cm/sec <br /> a <br />