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CONCLUSIONS <br /> The laboratory analytical results of the groundwater samples collected from all the monitoring wells, <br /> except MW5, in September and October 2005 are generally consistent with recent historical <br /> analytical results of groundwater samples collected from these wells. The concentrations of BTEX <br /> and TPHg detected in the groundwater sample collected from MW5 in September represent historical <br /> highs for these constituents. MW i and MW8 located in the central portion of the site are the most <br /> impacted wells. The concentrations of petroleum hydrocarbons detected in the groundwater samples <br /> collected from these wells in September decreased with respect to the previous sampling event, and <br /> the concentrations detected in the sample collected from MW8 represent historical lows. The <br /> concentrations of petroleum hydrocarbons detected in the groundwater sample collected from deep <br /> well MW7 in October decreased with respect to the previous sampling event and suggest that the <br /> vertical extent of impacted groundwater in the vicinity of this well is close to 120 feet bgs. <br /> The shallow groundwater plume appears to be adequately defined to the west and north in the <br /> ' vicinities of MW10 and MW11R, but is not defined to the east and south. The intermediate <br /> groundwater plume appears to be generally defined to the northwest in the vicinity of MW 12, but not <br /> well defined in other directions. Groundwater flow in the shallow zone was variable with eastward <br /> and northward components flowing toward the center of the site. Groundwater flow in the <br /> intermediate zone was towards the south. <br /> IP Additional investigation to the east and south is necessary to evaluate the extent of petroleum <br /> hydrocarbon impact. ATC is awaiting comment from the San Joaquin County Environmental Health <br /> Department regarding the Subsurface Investigation Workplan, dated October 31, 2005. <br /> Please contact our office at (209) 579-2221 if you have any questions or comments. <br /> ' Respectfully submitted, <br /> ATC Associates Inc. <br /> Todd Hafner, P.G. rol <br /> Professional Geologist ` '" <br /> Jea e Homsey, P.E. <br /> CA Registered Civil Engineer No. 47410 � '' ' .• <br /> sem• �1.y{.. <br /> cc: Mr. &Mrs. Ernest Foppiano <br /> Mr. Jim Barton, CRWQCB <br /> s;lenviromenta11283491reports12005 3QMR.doc 4 ATC Associates Inc. <br />