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' Third Quarter 2004 Groundwater Report
<br /> 8200 N Highway 99, Stockton, CA
<br /> Page 4 of 6
<br />' gradient downgradient of the extraction well was 0 0022 on September 14, 2004, or
<br /> approximately 11 5 feet per mile Table 4 summarizes groundwater elevations in site monitoring
<br /> wells Figure 3 presents a potentiometric surface map generated using the September 14, 2004
<br />' monitoring data Attachment G contains field notes
<br /> 4.2 Groundwater Sampling and Analysis
<br />' An experienced Ground Zero technician purged at least three well casing volumes of water from
<br /> monitoring wells MW2 through MW16 and well EW2 prior to sampling Samples were
<br />' collected from MW1 on July 16, September 1, and 15, 2004 as part of the treatment system
<br /> monitoring (samples designated INF, Table 1) The technician measured the temperature, pH
<br /> and electrical conductivity of the water during the purging process Purged groundwater was
<br />' contained in appropriately labeled DOT-approved 55-gallon drums in accordance with 49 CFR
<br /> part 172 and 40 CFR part 262, and will eventually be processed through the groundwater
<br /> treatment system Attachment G contains field purge logs
<br /> 1 Groundwater samples were collected after the physical parameters stabilized and water levels in
<br /> the wells recovered to 100% of their respective pre-purged levels The samples were temporarily
<br />' stored in an ice chest refrigerated to a temperature of approximately 4°C and delivered under
<br /> chain of custody protocol to Argon Laboratories (ELAP #2359) for analysis
<br /> Argon Laboratories analyzed all groundwater samples collected for total petroleum hydrocarbons
<br /> as gasoline (TPHg) using EPA 8015B, benzene, toluene, ethylbenzene, and total xylenes (BTEX)
<br /> using EPA 8021B, and oxygenated gasoline additives, ethylene dibromide (EDB), 1,2-
<br /> dichloroethane (1,2-DCA)using EPA 8260B
<br /> No gasoline constituents, including MTBE, were detected in the groundwater samples collected
<br />' from shallow aquifer wells MW7, MWS, MW10, MW11, MW15 or MW16 in September 2004 In
<br /> addition, no gasoline constituents or MTBE were detected in deeper zone wells MW9B, MW14B,
<br /> or MW13C
<br /> TPHg and BTEX constituents were detected in groundwater samples collected from wells MW1
<br /> and MW2 in September 2004 On September 15, 2004, well MW i contained TPHg at 44,000 parts
<br /> tper billion (ppb), benzene at 760 ppb,toluene at 5,500 ppb, ethylbenzene at 940 ppb, and xylenes at
<br /> 6,600 ppb Well MW1 was also sampled this quarter on July 16 and September 1, 2004 The
<br /> results for those sampling events are given on Table 5 Well MW2 contained TPHg at 190 ppb,
<br />' benzene at 13 ppb,toluene at 1 5 ppb, ethylbenzene at 4 9 ppb, and xylenes at 14 ppb
<br /> MTBE was present in wells MW1, MW2, MW3, MW4, MW5, MW6, MW12, and EW2 at
<br />' concentrations of 810 ppb, 110 ppb, 580 ppb, 2,700 ppb, 25 ppb, 24 ppb, 550 ppb and 140 ppb,
<br /> respectively No MTBE was detected in samples collected from wells MW7, MW8, MW9B,
<br /> MW10, MW11, MW13C, MW14B, MW15, or MW16
<br /> Table 5 summarizes groundwater analytical results Figures 4, 5 and 6 present isoconcentration
<br /> G 1GROUNl7ZE1TULEBURG1Repor.\QMR1200413QM2004 doc
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