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Is <br /> s. <br /> HIM <br /> PROBLEM ASSESSMENT REPORT <br /> Moore petroleum, Inc. <br /> 14800 U. Frontage Road, Manteca, CA <br /> MCA Project No. 10-90-47P <br /> Page 10 <br /> 3..6 Hvdrogeolovv <br /> Following the recent ground-water sampling event at the site the <br /> top of casing elevations for all monitoring wells have been re— <br /> surveyed .by :a California Registered Surveyor. Casing elevations <br /> as well as recent water level data are presented in Table 4. The <br /> most recent water level measurements at the site shows that the <br /> elevation of the ground-water surface beneath the site varies from <br /> a low of 8.86 feet mean sea level (msl) at MW-7 to a high of 9.54 <br /> feet msl at MW-5. A water table contour map, based on the August <br /> 23, 1990, water level monitorir-q event is shown as Figure 6. The <br /> ground water contour map indicates that the direction .of; ground <br /> water'-luw is generally East and Northeast across the site. Thisre <br /> is a sigiliLicant bend in ground-water contours along a line running <br /> " approximately between well MW-4 and mw-8. The change in the <br /> direction of ground-water flow along this line may be due to the <br /> presence of the leach field along the southern border of the site <br /> (Figure 6) . The leach field may be providing sufficient recharge <br /> to the shallow ground-water system to alter the direction of <br /> ground-water flow in its vicinity. The hydraulic gradient at the <br /> site along a line running approximately from MW-5 to MW-1 is about <br /> .005 foot/foot. The average hydraulic conductivity of the water <br /> r bearing sediments at the site was reported in Delta's Prelil mi�nary <br /> H droaealo is Assessment Report as 6.28 feet/day. This hydraulic <br /> conductivity value was determined by analysis of slug tests which <br /> were pe,7formed in monitoring weiis Mw-1, mW-2, MW-3, and MW-4. The <br /> average ground water velocity at the site can be estimated from the <br /> following equation: <br /> v = Kr <br /> n <br /> Where V = Average linear velocity <br /> K = Hydraulic conductivity <br /> I = Hydraulic gradient <br /> n = porosity <br /> - at the site: V = 6.29 feet da .005 foot foot <br /> 0.25 <br /> V = .125 feet/day = 45.84 feet/year <br /> NOTES: <br /> n is estimated <br /> K is averaged <br /> The average linear.-velocity.-may_. change-periodically-due to--changes <br /> fluctuations. - <br /> fn a hydraulic gradient caused by seasonal ground water level <br /> J <br />