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PRELIMINARY HYDROGEOLOGIC ASSESSMENT REPORT <br /> i 5491 'F Street, Banta, Califomia <br /> Delta Project No. 40-M-481 <br /> Page 8 <br /> f <br /> 1 <br /> The depth to the ground water measured on May 24, 1989, ranged from 11.94 to 11.54 feet below grade. <br /> The ground water contour map (Figure 7) indicates ground water flow to be in an eastward direction at <br /> a gradient of about 0.004 foot/foot. To determine the hydraulic conductivity of the water bearing sediment <br /> at the site, a slug test was performed in each monitoring well. The data was evaluated using methods <br /> presented by Bower and Rice (1976). The results of the slug tests are summarized in Table 6. Hydraulic <br /> 5 <br /> conductivity values ranged from 3.71 feet/day (MW-1) to 6.52 feet/day (MW-3). The average K value <br /> for the formation is 5.18 feet/day. The average ground water velocity at the site is 0.068 feet/day, based <br /> on the average K value (5.18 feet/day), and an estimated porosity of 30 percent. <br /> The average velocity of 0.068 feet/day was derived from the following equation: <br /> t <br /> yr <br /> V — KI <br /> n <br /> -Where V= Average linear velocity. <br /> K= Hydraulic conductivity. <br /> I = Hydraulic gradient. <br /> n = Effective porosity. <br /> At the site: V= f5.18 feet/day) (0.004 foot/feet) <br /> 030 <br /> k ; <br /> V 0.068 feet/day = 25.2 feet/year <br /> NOTES: <br /> n - Estimated. <br /> K ° Averaged. <br /> The average linear velocity is expected to periodically shift with hydraulic gradient changes related to <br /> seasonal ground water level fluctuations. <br /> I <br /> i <br /> I <br /> i <br />