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CLEARWATER <br />' G R O U P, I N C <br /> ElIDLIGnMertlal Services <br /> 13 Groundwater Flow Direction and Gradient <br />' On January 20, 1999, depth to groundwater ranged from 7 69 to 8 45 feet below top of casing On March <br /> 23, 1999, depth to groundwater ranged from 8 76 to 9 18 feet below top of casing These results indicate a <br />' southeasterly groundwater flow direction at a gradient of approximately 0 005 ft/ft in January for MW- <br /> 4, -5 and -6, and 0 01 ft/ft in March for MW-1, -2 and -3 Gauging data is presented in Table 2 and <br /> Appendix C Groundwater elevation contours are shown on Figure 5A and 5B <br /> I <br /> 3 4 Groundwater Sample Analytical Results <br />' TPHg and BTEX were detected in concentrations exceeding method detection limits in groundwater <br /> samples collected from all monitoring wells sampled on January 20 and March 23, 1999 Concentrations <br />' of analytes were highest in MW-5, which is assessed as downgradient of the former UST pit <br /> Concentrations of TPHg and benzene in MW-5 were 48,000 gg/L and 6,200 gg/L,respectively MTBE was <br />' detected in four of the six sampled wells in concentrations up to 61 gg/L (MW-6) Detection limits for <br /> MTBE in MW-5 were elevated above normal Dissolved hydrocarbon concentrations are summarized in <br /> Table 2 and are shown on Figure 6 The certified laboratory analytical report is presented with the <br />'. chain of custody in Appendix D <br />' 3 5 Sensitive Receptor Results <br /> The review of DWR well records indicated the presence of one water-supply well located within the <br /> t search area The well is located immediately to the north of Barnes Trucking, at the southwest corner <br /> k <br /> of the intersection of Charter Way (Route 4) and Fresno Avenue (Figure 1) This location is upgradient Z �� <br /> of the contamination source on the Barnes Trucking property at a distance of approximately 400 feet Z <br /> The well was installed to supply water for industrial use, however, the property has now been <br /> redeveloped with housing Well construction and use data are sumarized on T <br /> mable 33 <br /> Review of the USGS topographic map for west Stockton, indicates that no potential surface water <br />' receptors exist within the search area Results of the survey therefore indicate that the hydrocarbon <br /> plume poses little or no threat to sensitive receptors in the vicinity at the current time <br />' C-178 WELL Ii isr RPT 5 May 7, 1999 <br />