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' <br /> ARCO Products Company 4 <br /> ARCO 4932, 16 E Harding Way,Stockton CA November 6 2000 <br /> • Stockpiled Soil <br /> Approximately 4 cubic yards of soil generated during the installation of the five wells <br /> was stockpiled onsite One composite sample (4 sleeves to 1 sample) was collected <br /> 1 from the stockpiled soil and analyzed for TPHg, BTEX, MtBE, and total lead Soilwas <br /> disposed of at Forward Landfill In Manteca, California Stockpiled soil analytical data <br /> 1s presented 1n Table 4 <br /> SUMMARY OF FINDINGS <br /> • TPHg was detected 1n 10 of 23 samples analyzed at a maximum <br /> concentration of 4,190 mg/kg (MW-4@ 15') Benzene was detected <br /> in 11 of 23 samples analyzed at a maximum concentration of 15 6 <br /> ' mg/kg (MW-4@25') MtBE was detected by EPA Method 82601n 11 <br /> of 23 samples analyzed at a maximum concentration of 684 mg/kg <br /> (MW-4@25') TAME was reported 1n three samples at a maximum <br /> ' concentration of 0 459 mg/kg (MW-4@25') Fuel oxygenates TBA, <br /> DIPE, EtBE, EDB and 1,2-DCA were not detected 1n the samples <br /> ' analyzed <br /> • TPHg, benzene, and MtBE were reported in groundwater samples <br /> from all wells at concentrations up to 166,000 ppb, 10,400ppb, and <br /> ' 708,000 ppb, respectively (MW-4) Fuel oxygenates TAME and 1,2- <br /> DCA were reported 1n all wells except MW-3 at maximum <br /> ' concentrations of 427 ppb (MW-4) and 23 8 ppb (MW-4), <br /> respectively TBA was reported 1n wells MW-2 (215 ppb) and MW-4 <br /> MW-4 (26,100 ppb) EtBE was reported 1n well MW-4 at a <br /> concentration of 2 22 ppb <br /> • Groundwater flow was to the northeast with a gradient of 0 009 ft/ft <br /> ' • The closest wells identified from DWR file review are wells located <br /> approximately 1/2 mile east of the site at the Stockton State Hospital <br /> ' CONCLUSIONS AND RECOMMENDATIONS <br /> Based on the data collected during this assessment, petroleum hydrocarbons have <br /> ' impacted both soil and groundwater beneath the site Impact to soil and groundwater <br /> was not defined during the most recent assessment activities To confirm <br /> ' concentrations of hydrocarbons In groundwater and groundwater flow direction, <br /> SECOR recommends the site be placed on a quarterly sampling schedule <br /> Additionally, given the concentrations of MtBE in groundwater, SECOR recommends <br /> the following <br /> ' 077 41983 3301well install <br />