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Atlantic Richfield Company 6 ARCO 595,6100 North Highway 99,Stockton Cahfomia September 13 2002 • (Figure 7) Groundwater elevation data are presented in Table 2 Historical shallow groundwater gradient data are included in Table 5 The groundwater gradient within the deeper water-bearing zone will be confirmed during subsequent quarterly groundwater monitoring events Stockpiled SoiMrge and Rinsate Water Approximately 17 cubic yards of soil generated during the installation of the wells was stockpiled on-site One composite sample (4 sleeves to 1 sample) was collected from the stockpiled soil, and analyzed for TPHg and BTEX by the DHS/LUFT method, and total lead by EPA Method 6010B TPHg and BTEX constituents were not detected in the stockpiled soil sample Total lead was detected at a concentration of 6 8 mg/kg Soil was transported from the site by Dillard Environmental to Altamont Landfill in Livermore, California on July 10, 2002 Analytical data for the stockpiled soil are presented in Table 6 Eight 55-gallon steel drums of nnsatelpurge water were stored on-site The nnsate/purge water was transported from the site by Dillard Environmental to Altamont Landfill in Livermore, California for disposal on July 30, 2002 SUMMARY OF FINDINGS • TPHg, BTEX,TPHd, MtBE, and fuel oxygenates were not detected in soil samples collected from the borings for shallow wells MW-8 through MW-10, and deep wells DMW-1 through DMW-3 • TPHg and benzene were not detected in groundwater samples from shallow wells MW-8 through MW-10, and deep wells DMW-1 through DMW-3 Trace levels of toluene were detected up to 2 6 ppb 1n wells MW-8, and DMW-1 through DMW-3 A minor concentration of ethylbenzene was detected in well DMW-1 at 0 51 ppb Minor concentrations of xylenes were detected in deep wells DMW-1 through DMW-3 at concentrations up to 2 8 ppb Minor concentrations of BTEX were also detected in the quality control blank • Concentrations of MtBE were detected in groundwater samples collected from shallow wells MW-8, MW-9, and deep wells DMW-1 through DMW-3 at concentrations up to 53 ppb (EPA Method 8260B) TBA was detected in deep wells DMW-1 through DMW-3 at concentrations up to 72 ppb Shallow well MW-8 and deep wells DMW-1 through DMW-3 contained concentrations of 1,2-DCA up to 4 6 ppb Other fuel oxygenates were not detected e Groundwater flow within the shallow water bearing zone on-site was to the northwest at a gradient of 0 003 ft/ft, groundwater flow within the shallow water bearing zone off-site was t0 the north-northeast at a I 1ARC010595\Reportslwe11 msta113 doc