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't <br /> PROBLEM ASSESSMENT REPORT <br /> Moore Petroleum, Inc. <br /> 9399 E. Yosemite Avenue, Mantecc, CA <br /> NGA Project No. 10-90-480 <br /> Page 9 <br /> 3.6 Hydrogeolog <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 3. 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 15.89 feet mean sea level (msl) at MW-3 to a high of 15.95 <br /> - feet msl at NW-2. A water table contour map, based on the August <br /> 27, 1990, water level monitoring event is shown as Figure 6. The <br /> ground water contour map indicates that ground--water elevation <br /> varies little across the site and that the direction of ground <br /> water flow is almost due West across the site. <br /> The hydraulic gradient at the site is low, on the order of a`aout <br /> .001 foot/foot. The average hydraulic conductivity of the water- <br /> bearing sediments at the site, as determined from slug tests <br /> conducted by Delta is 0.56 feet/day. The average linear velocity <br /> of ground-water flow at the site can be estimated from the <br /> following equation: <br /> V = KI <br /> n <br /> Where V = Average linear velocity <br /> K = Hydraulic conductivity <br /> T = Hydraulic gradient <br /> n = porosity <br /> at the site: V = (0.56 feet/day) (.001 foot/foot). <br /> " 0.25 <br /> V = 0.81 foot/year <br /> NOTES: <br /> n is estimated <br /> K is averaged <br /> The calculated average linear is very low, but appears to reflect <br /> the predcninantly fine-grained sediments encountered at the site <br /> and the very low hydraulic gradient. The ground-water velocity may <br /> change periodically clue to changes in the hydraulic gradient caused <br /> --- --.-----------..._-------by._-seasonal-.ground-water--level-fluctuations.----......-- <br />