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C#010gical Technics lnc. Page 8 <br /> Site Conceptual Model <br /> Project No. 989.2 <br /> December 17,2003 <br /> ' mile north of the Stockton Deep Water Channel (Figure 1). West Oak Street borders the <br /> property to the north and West Fremont Street to the south. <br /> ' Infiltration of surface water at and around VWDC is impeded. Areas not occupied by <br /> structures are capped in asphalt at the property and adjoining properties. Valley Wholesale <br /> ' Drug Company has a few planting areas in the parking lot with trees and shrubs planted in <br /> uncovered soil. This uncovered soil occupies a negligible area and should not have a <br /> significant impact on infiltration. <br /> ' 4.2 Hydrogeology of Site <br /> ' A site-specific groundwater gradient and bearing was calculated from the depth to water <br /> measurements taken during the September 2, 2003, groundwater monitoring event. The <br /> bearing was N38°E and the gradient was 0.0051 ft/ft. The average groundwater elevation <br /> ' recorded at the site for this monitoring event was 1.20 feet below mean sea level. Gradient <br /> calculations at the site are consistent with those previously recorded for the Valley Wholesale <br /> Drug Company site. <br /> The historical average depth to water is 8.14 feet below top of casing. The historical average <br /> groundwater elevation is 0.67 feet below mean sea level. The average groundwater bearing <br /> and slope recorded at the site are N28°W and 0.0067 ft/ft respectively. A summary of <br /> groundwater elevation and gradient is attached as Table 3 in Appendix A. Figure 3 is a rose <br /> ' diagram showing historical groundwater bearing and slope. <br /> Vertical groundwater gradients were calculated for the site using the MW-1/MW-101 well <br /> ' pair and found to be negative, indicating a downward component to contaminant migration. <br /> MW-1 is screened from 5 to 25 feet bgs and MW-101 is screened from 29.5 to 42 feet bgs. <br /> The vertical gradient is approximately two orders of magnitude greater than the horizontal <br /> gradient during the September 2003 groundwater-monitoring event. A summary of vertical <br /> groundwater gradients is attached as Table 4 in Appendix A. <br /> 1 <br /> 1 <br /> 1 <br /> l <br />