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Atlantic Richfield Company 3
<br /> Former ARCO 4493,205 N.Center Street.Stockton.CA sC 1011111cr 5,2000
<br /> In wells MW-5 through MW-7, silty clay was encountered from approximately 4 to 6 feet
<br /> bgs to a depth of I i feet bgs. Silty sand to sand was encountered below the silty clay
<br /> from approximately 1 I to 25 feet bgs Groundwater was encountered within the silty
<br /> sand to sand at depths of approximately 13 to 15 feet bgs
<br /> Within all four borings the upper 4 to 10 feet of soils encountered was likely fill material.
<br /> Groundwater monitoring wells were installed within the shallow borings upon completion
<br /> of the drilling (MW-5 through MW-7). Boring B-I was backfilled with grout from the
<br /> bottom of the boring to the ground surface upon the completion of drilling.
<br /> Soil Sampling and Analysis
<br /> Soil samples were collected continuously in boring B-1 and at 5-foot intervals in wells
<br /> MW-5 through MW-7. Selected samples were analyzed for TPHg by EPA Method 8015,
<br /> benzene, toluene, ethylbenzene, xylenes (BTEX), and MtBE by EPA Method 8020, and
<br /> fuel oxygenates (MtBE, TAME, DIPS, EtBE, TBA, EDB, and 1,2-DCA) by EPA
<br /> Method 8260. Additionally, selected soil samples from boring B-I were analyzed for
<br /> volatile organic compounds (VOCs) by EPA 8260.
<br /> TPHg was detected in sample B-1 (325' at a concentration of 47.9 mg/ko. MtBE was
<br /> reported in sample B-1 :e)16' at a concentration of 0.254 mg/kg. t-uel oxygenates TAME,
<br /> DIPE, EtBE, TBA, FDB and 1,2-DCA were reported as nondetect in all soil samples
<br /> • analyzed. Several VOCs were reported in sample B-1@25' as summarized in Table 1.
<br /> No detectable concentrations of hydrocarbons were reported soil samples from wells
<br /> MW-5 through MW-7. Soil analytical results are presented in Table 1 . Field and
<br /> laboratory procedures are presented as Attachment D. Certified analytical reports and
<br /> chain-of-custody documentation are presented as Attachment E.
<br /> Groundwater "Grab" Sampling
<br /> Groundwater "grab" samples were collected from boring B-I at depths of 30, 45, and 60
<br /> feet bgs on May 8, 2000. The samples were analyzed for TPHg by EPA Method 8015,
<br /> BTEX, and MtBE by EPA Method 8020, and fuel oxygenates (MtBE, TAME, DIPE,
<br /> EtBE, TBA, EDB, and 1,2-DCA) by EPA Method 8260.
<br /> TPHg, benzene, and MtBE were detected in all three "grab" samples from boring B-1.
<br /> Concentrations of TPHg, benzene, and MtBE at 60 feet bgs were 663 ppb, 56.4 ppb, and
<br /> 28.8 ppb, respectively.
<br /> Groundwater Monitoring Well Development, Sampling, and Stirveying
<br /> After installation, the groundwater monitoring wells were developed by rigorously
<br /> surging over the length of the screen interval and by purging approximately ten casing
<br /> volumes of water.
<br /> Groundwater samples were collected from the newly installed groundwater monitoring
<br /> wells on June 16, 2000. Groundwater samples were analyzed for TPHg, BTEX, and
<br /> MtBE by EPA Method 8015/8020 and VOCs by EPA Method 8260.
<br /> 077.41883.3301wcll install2.doc
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