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Report_ Groundwater-quality Monitoring—October 25,2002: 7500 West Eleventh Street,Tracy, C4. Page 7 <br /> Assume relative proportions of diesel and gasoline in the floating product in Monitoring <br /> Well MW-7 are in the same ratio as the concentrations of diesel and gasoline in the <br /> sample of groundwater recovered from that well on December 13 p g , 2001. They were, <br /> ' respectively, 800,000 µg/L and 61,000 µg/L. (See Table 2.) <br /> Thus, the estimated specific gravity of the floating product in well MW-7 is: <br /> = <br /> pp = 0.83 <br /> ' The depression in the elevation of the water table due to the presence of floating product <br /> is given by: <br /> W=T(pp/pH,) (Equation 1) <br /> Where: <br /> W= the depression of the water table <br /> T = the thickness of floating product in the monitoring well <br /> pW = the specific gravity of the groundwater <br /> PP= the specific gravity of the floating product <br /> Thus, in the case of the floating product measured in well MW-7 on October 25, 2002: <br /> W=0.48 (0.8311.0) = 0.40 ft. <br /> Accordingly, when drawing the contours shown on Figure 2, the elevation of the <br /> =``' groundwater in well MW-7 was based on an assumed depth to groundwater of 9.44 ft. <br /> rather than the depth of 9.84 ft. actually measured. This yields a corrected groundwater <br /> table elevation of 38.78 ft. MSL (which is shown on Figure 2) compared to the <br /> uncorrected value of 38.38 ft MSL given in Table 1. <br /> '-_- In addition, the groundwater elevations in Wells MW-3A, MW-3B and MW-12A were <br /> not considered when the groundwater contours were drawn because, although small in <br /> magnitude, differences between the elevations of the groundwater in wells MW-3, MW- <br /> a3A and MW-3B and in MW-12 and MW-12A are sufficiently great to indicate that the <br /> groundwater monitored by the shallow well at the locations of each of those well clusters <br /> has different pieziometric pressures than that of the deeper wells in the same cluster and <br /> } 1 therefore must be assumed, at least locally, to monitor aquifers different from that <br /> i monitored by the shallow wells. <br /> On October 25, 2002, the mean groundwater gradient in the shallow, near-surface aquifer <br /> jjbeneath the site was approximately 0.003 ft/ft. Although there were some minor changes <br /> sic <br />