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Geological Technics Inc. <br /> 1101 7`h Street <br /> Modesto,California 95354 <br /> (209)522-4119/Fax(209)5224227 <br /> Additional Site Characterization Report - <br /> ' Soil and Groundwater Investigation <br /> ' Morita Brothers <br /> 814 E. Charter Way <br /> ' Stockton, CA <br /> Project No 7243 2 <br /> ' Apnl 19, 2004 <br /> ' EXECUTIVE SUMMARY <br /> Geological Technics Inc has prepared the attached Report summarizing the fieldwork <br /> completed on December 15 - 23, 2003 This work involved the installation of nine new <br /> monitoring wells to further define the lateral extent of the groundwater plume <br /> ' No field evidence of contamination was noted above the water table in the six new wells <br /> installed to the east of the site - the historical down gradient direction Faint odors <br /> resembling a sewage or organic odor were noted in the submerged portion of the boreholes <br /> for well pairs MW-1081208 and MW-1091209 No evidence of contamination was noted in <br /> ' the MW-1101210 well pair location <br /> Groundwater monitoring data (Table 1) suggest that a submerged plume extends off site at <br /> ' depths beneath the current water table at approximately 38 feet below grade surface When <br /> the first quarter 2004 groundwater monitoring/sampling event is completed, the mass of the <br /> groundwater contamination can be calculated This data will be evaluated to determine if an <br /> engineered clean up of the residual gasoline contamination is warranted <br /> In addition, the sampling of wells MW-111111 will reveal whether or not any off site <br /> gasoline contamination is migrating to the Morita property and producing a "co-mingled" <br /> ' plume <br /> ' 1.0 SITE HISTORY <br /> In December 1991, four underground storage tanks (USTs) were removed from the site <br /> ' (Figure 1) Gasoline range petroleum hydrocarbons were detected in shallow soils beneath <br /> the tanks and seven soil borings were installed in March 1992 to further define the extent of <br /> the contamination The borings revealed low to moderate concentrations of benzene, <br /> toluene, ethylbenzene and xylene (13TEX), and gasoline range petroleum hydrocarbons <br /> (TPH-Gasoline) in soils up to 50 feet below grade surface (bgs) In March 1993, shallow <br /> 1 <br />