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I <br /> qe0bg1cal Technics lac. <br /> 11017"'street <br /> Modesto,California 95354 <br /> (209)522-4119/Fax#522-4227 <br /> L Additional Site Characterization Work Plan <br /> Cone Penetrometer Testing <br /> Morita Brothers k <br /> 81.4 E. Charter Way <br /> . Stockton, CA <br /> Project No. 724.2 <br /> March 8, 2005 <br /> LO INTRODUCTION <br /> LIn December 1991, four underground storage tanks (USTs) 'were removed from the site. <br /> (Figure 2). 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 /> C the contamination. The borings revealed low to moderate concentrations of benzene, toluene, <br /> ethylbenzene and xylene (BTEX), and gasoline range- petroleum hydrocarbons (TPH- <br /> LGasoline) in soils up to 50 feet below grade surface (bgs).'"Tn March 1993, shallow soils from <br /> beneath the former USTs and product piping areas were excavated for disposal. The ' <br /> resulting excavations were advanced to depths of 20-28. feet bgs, which generated <br /> f approximately 750 cubic yards of.soil for disposal. <br /> L I <br /> Three monitoring wells (MW-1 through. MW-3) were installed in September 1992 to <br /> determine if groundwater had been impacted by the release-- see Figure 2 for well locations. <br /> Groundwater samples obtained from the wells confirmed that BTEX and TPH-G were <br /> r present and the contaminant concentrations exhibited minor fluctuations during 18 <br /> monitoring events conducted between 1992 and 1999. '''ITwo additional monitoring wells <br /> (MW-4 and MW-5) were installed in September 1999, and incorporated into the monitoring <br /> schedule. Samples obtained in November 1999 and 'March 2000, from well MW-4, <br /> . <br /> contained elevated levels of benzene and TPH-G for the two events. <br /> On November 20 _ 22, 2000, five additional groundwater;monitoring wells were installed to i <br /> L investigate the lateral and vertical extent of gasoline-range petroleum hydrocarbons in the j <br /> groundwater: MW-6, MW-7, MW-104, MW-106 and MWS 107 (Figure 2). Wells MW-6 and E <br /> MW-106 were placed,on the adjacent parcel to the east of the site, approximately 60 feet <br />