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' ARCO Products Company 2 ARCO 4932 16 E Harding Way,Stockton CA November 6 2000 1� • were reported in one sample each at concentrations of 102 mg/kg (T-2S @ 19') and ' 0 579 mg/kg (T-3S@19'), respectively Benzene and fuel oxygenates were reported as nondetect in all samples from the UST after over-excavation Approximately 150 tons of soil was over-excavated from the product line and dispenser areas TPHg was ' reported in three of six samples taken from these areas at a maximum concentration of 5,430 mg/kg (D4@ 11') Benzene was reported in two samples at a maximum concentration 10 6 mg/kg (D4@ 11') MtBE was reported in two samples at a maximum ' concentration of 55 5 mg/kg (D5@8 5) ' ASSESSMENT ACTIVITIES AND FINDINGS On August 21 and 22, 2000, three groundwater monitoring wells (MW-1, MW-2, MW-3), ' one groundwater monitoring/vapor extraction well (MW-4), and one vapor extraction well (SVE-1) were completed at the site by West Hazmat Drilling of Rancho Cordova, California Groundwater monitoring wells MW-1, MW-2 and MW-3 were set at 40 feet ' bgs and screened from 10 to 40 feet bgs Groundwater monitonng/vapor extraction well (MW-4) was set at 40 feet bgs and screened from 5 to 40 feet bgs Vapor extraction well SVE-1 was set at 30 feet bgs and screened from 5 to 30 feet bgs Boring Logs showing ' well completion details are included as Attachment B The findings of this assessment are discussed below Subsurface Conditions lie In each of the borings, interbedded layers of fine-grained sand to sandy silt and sandy to silty clay were encountered from ground surface to the total depth of the borings Groundwater was encountered at approximately 28 feet bgs ' Soil Sampling and Analysis Soil samples were collected at 5-foot intervals using a split spoon sampler Selected samples were analyzed for TPHg by EPA Method 8015, benzene, toluene,ethylbenzene, ' xylenes (BTEX), and MtBE by EPA Method 8020, and fuel oxygenates methyl tert- butyl ether(MtBE), tert-amyl methyl ether(TAME), di-isopropyl ether (DIPE), ethyl ' tert-butyl ether(EtBE), tert-butyl alcohol (TBA), ethylene di bromide (EDB), and 1,2- dichloroethane (1,2-DCA) by EPA Method 8260 TPHg was detected in 10 of 23 samples analyzed at a maximum concentration of 4,190 ' mglkg(MW-4@ 15') Benzene was detected in 11 of 23 samples analyzed at a maximum concentration of 15 6 mglkg (MW-4@25') MtBE was detected by EPA ' Method 8260 in 11 of 23 samples analyzed at a maximum concentration of 684 mg/kg (MW-4@25') TAME was reported in three samples at a maximum concentration of 0 459 mg/kg (MW-4@25') Fuel oxygenates TBA, DIPE, EtBE, EDB, and 1,2-DCA ' were reported as nondetect in the 23 samples analyzed Soil analytical results are presented in Table 1 Field and laboratory procedures are presented as Attachment C 1 ' 077 41983 330/well install