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s <br /> Atlantic Richfield Company 3 <br /> ARCO 5450, 1617 West Fremont Street,Stockton,CA April 10,2002 <br /> • Subsurface Conditions <br /> In each of the borings, sand was encountered from ground surface to approximately 6 <br /> feet bgs. Beneath the sand, clayey silts and silty clays were present through the <br /> remainder of the borings. Groundwater was encountered in clayey silt at approximately <br /> 12 to 13 feet bgs. <br /> Soil and Groundwater Sampling and Analysis <br /> Soil samples from the three soil borings were collected at five-foot intervals by a <br /> California split-spoon sampler. Selected soil samples were analyzed for TPHg by EPA <br /> Method 8015, BTEX by EPA Method 8020, and fuel oxygenates, including methyl tert- <br /> butyl ether (MtBE), tertiary amyl methyl ether(TAME), di isopropyl ether (DIPE), ethyl <br /> tertiary butyl ether (EtBE), tertiary butyl alcohol (TBA), ethylene dibromide (EDB), and <br /> 1,2-dichloroethane (1,2-DCA) by EPA Method 826413. <br /> MtBE by EPA Method 8260B was reported in two soil samples from soil boring SB-1 at <br /> concentrations of 0.0079 mg/kg (SB-1@15') and 0.011 mg/kg (SB-1@20'). TPHg, <br /> benzene, and fuel oxygenates (MtBE, TAME,DIPE, EtBE, TBA, EDB and 1,2-DCA) <br /> were reported as nondetect in all other soil samples analyzed. Soil analytical results are <br /> presented in Table 1. Field and laboratory procedures are presented as Attachment C. <br /> Certified analytical laboratory reports and chain-of-custody documentation are presented <br /> as Attachment D. <br /> Additionally, three groundwater samples (SB-1, SB-2, and SB-3) were collected from <br /> the soil borings with a hydro-punch sampling device and analyzed for the same <br /> constituents listed above. Hydra-punch water samples were collected at depths of 22 <br /> feet (SP-1 and SP-2) and 15 feet (SP-3). Laboratory analysis reported MtBE by EPA <br /> Method 8260B in all three samples at concentrations of 3.7 µg/L(SB-2), 43 gglL(SB-3), <br /> and 68 µg/L (SB-1), respectively. TBA was reported in SB-3 at a concentration of 24 <br /> µg/L. Toluene was reported in SB-2 at a concentration of 4.4 µglL and xylenes (total) <br /> were reported in SB-1 at a concentration of 0.68 µg/L. All other analytes were reported <br /> below laboratory detection limits. Groundwater analytical data is presented in Table 2 <br /> and shown on Figure 2. <br /> Stockpiled Soil <br /> Approximately 3 cubic yards of soil generated during the installation of the wells was <br /> stockpiled onsite. One composite sample (4 sleeves to 1 sample) was collected from the <br /> stockpiled soil and analyzed for TPHg, BTEX, and total lead by methods described in <br /> Attachment C. Soil was disposed of at Forward Landfill in Manteca, California. <br /> Stockpiled soil analytical data is presented in Table 3. <br /> 77BP.43323.00.02301site assessment.doc <br />