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' ARCO Products Company 3
<br /> ARCO 4932, 16 E Harding Way Stockton CA November 9 2001
<br />' - --ASSESSMENT A TI - - - - - - —- -- - - — - - ---
<br /> �-•- C VITIES AND FINDINGS
<br /> ' From duly 9 to July 16, 2001, West Hazmat Drilling of Rancho Cordova, California drilled
<br /> two soil borings and five groundwater monitoring wells at the site Soil borings SB-I and
<br /> SB-2 were drilled to 80 feet and 78 feet bgs, respectively Monitoring wells MW-5, MW-
<br /> 6, MW-7, MW-8, and MW-9 were installed at 40 feet bgs Each of the wells was screened
<br /> from 20 feet bgs to 40 feet bgs Well completion details are included in Table 1
<br /> ' Locations of the soil bonngs and monitoring wells are shown on Figure 2
<br /> Subsurface Conditions
<br /> ' In each of the borings, interbedded layers of sandy silt and silty clay were encountered
<br /> from ground surface to approximately 20 feet bgs Below 20, the soil was comprised of
<br /> fine-grained sands and silt mixtures to the total depth of the borings Groundwater was
<br /> ' encountered at approximately 27 feet bgs Generalized geologic cross-sections are
<br /> included as Figures 3 and 4
<br /> ' Soil Sampling and Analysis
<br /> Bonngs SB-1 and SB-2 were continuously cored for logging and soil samples were
<br /> i ' collected for analysis Soil samples from the monitoring wells were collected at 5-foot
<br /> intervals using a California modified splitspoon sampler Selected samples were
<br /> • analyzed for TPHg and benzene, toluene, ethylbenzene and xylenes (BTEX) by a
<br /> ' California Department of Health Services/Leaking Underground fuel tank (DHS/LUFT)
<br /> method, and fuel oxygenates including MtBE, TAME, di-isopropyl ether(DIPE), EtBE,
<br /> ' TBA, ethylene dibromide (EDB), and 1,2-DCA were analyzed by EPA Method 8260
<br /> Soil analytical results are summarized in Table 2 and shown on generalized geologic
<br /> cross sections (Figures 3 and 4) Five of 35 samples analyzed contained detectable
<br /> ' constituents TPHg and benzene were detected in one of the 36 samples analyzed at
<br /> concentrations of 6 9 mg/kg and 0 12 mg/kg, respectively(SB-2, 26 5') Toluene was
<br /> ' detected in two samples at concentrations of 0 0056 mg/kg (MW-6, 15') and 0 0051
<br /> mg/kg (MW-6, 29') Xylenes were detected at a maximum concentration of 0 15 mg/kg
<br /> (SB-2, 26 5') EPA Method 8260 detected MtBE in two soil samples at a maximum
<br /> ' concentration of 8 2 mg/kg (MW-6, 40') No ethylbenzene ,TAME, TBA,DIPE, EtBE,
<br /> EDB, or 1,2-DCA were detected in the 36 samples analyzed Field and laboratory
<br /> procedures are presented as Attachment C Certified analytical reports and chain-of-
<br /> custody documentation are presented as Attachment D
<br /> Depth Discrete Groundwater "Grab" Samples
<br /> ' Depth discrete groundwater"grab" samples were collected using a HydropunchTM
<br /> technique from boring SB-1 at depths of 33, 48, and 68 feet bgs and from SB-2 at
<br /> ' depths of 33, 50, 65, and 77 feet bgs The groundwater samples were analyzed for
<br /> • TPHg, BTEX, and MtBE using a DHS/LUFT method and fuel oxygenates TBA, MtBE,
<br /> DIPE, EIBE, TAME, 1,2-DCA, EDB, and ethanol using EPA Method 8260AM
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<br /> ' 077 43826 330lAddAssess doe
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