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Report: Groundwater-qualio,Monitoring—January 20,2003: 7500 West Eleventh Street, Tracy, CA. Page 7 The groundwater elevations presented in Table 1 were used to generate the groundwater ' contours shown on Figure 2. However, because, as is noted in Table 2, an apparent 0.32 .t ft. of floating product was detected in Monitoring Well MW-7, the groundwater elevation in that well was corrected for the purpose of drawing the groundwater contours to allow for the depression of the water table in the vicinity of that well by the hydrocarbon fuel i products floating on the surface of the water. The correction was derived as follows: Assume Specific Gravity of Diesel= 0.84 Assume Specific Gravity of Gasoline= 0.74 Assume relative proportions of diesel and gasoline in the floating product in Monitoring } Well MW-7 are in the same ratio as the concentrations of diesel and gasoline in the sample of groundwater recovered from that well on December 13, 2001. They were, respectively, 800,000 µg/L and 61,000 µg/L. (See Table 2.) Thus, the estimated specific gravity of the floating product in well MW-7 is: PP = 0.83 The depression in the elevation of the water table due to the presence of floating product is given by: W=T (pp/PW) (Equation 1) Where: W= the depression of the water table T = the thickness of floating product in the monitoring well pW = the specific gravity of the groundwater Pp= the specific gravity of the floating product 4'.<. Thus, in the case of the floating product measured in well MW-7 on January 20, 2003: W= 0.32 (0.83/1.0) = 0.27 ft. Accordingly, when drawing the contours shown on Figure 2, the elevation of the groundwater in well MW-7 was based on an assumed depth to groundwater of 9.33 ft. rather than the depth of 9.60 ft. actually measured. This yields a corrected groundwater table elevation of 38.89 ft. MSL (which is shown on Figure 2) compared to the uncorrected value of 38.62 ft MSL given in Table 1. 1 sic