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x, rJ Mr Harlin Knoll Page 2 of 3 (bgs) in well MW3 to 33 33 feet bgs 1n well MW2 Groundwater elevations in site wells rose an average of 2 97 feet between November 9, 2001 and February 8, 2002 The water table beneath the site lies above the screened intervals in wells MW I, MW2, MW4 and MW5 Monitoring well construction details are summarized in Table 1 and groundwater monitoring data are summarized in Table 2 Groundwater flow in the vicinity of the former USTs was toward the east with a gradient of 0 0018 or approximately 9 5 feet per mile A potentiometric surface map for February 8, 2002 is presented on Figure 2 An experienced Ground Zero technician purged a minimum of three well casing volumes of groundwater from monitoring wells MW1, MW3, MW4 and MW5 on February 8, 2002 The wells were purged using an electric, submersible pump During the purging process the temperature, specific conductance, and pH of the water were measured and recorded All downhole equipment was decontaminated prior to and between wells using a solution of laboratory-grade detergent, then double-nnsing in separate containers of clean rinse water Groundwater samples were collected using dedicated, disposal bailers after physical parameters stabilized The samples were decanted into preserved 40-m1 glass vials and placed in an ice chest refrigerated to a temperature of at approximately 4°C The samples were transported to Argon Laboratories (FLAP 92359) under chain of custody protocol and analyzed for TPHg and BTEX utilizing EPA methods 8015M and 8020, respectively Purged groundwater and decontamination rinse water were contained in labeled Department of Transportation (DOT) approved drums pending disposal Copies of field purge logs and water level measurements are included in • Attachment B Purgewater Disposal On March 15, 2002, American Valley Waste Oil removed and transported approximately 300 gallons of purgewater to Seaport Environmental located in Redwood City, CA for disposal Documentation is included in Attachment A Groundwater Analytical Results Elevated levels of dissolved gasoline constituents were detected in the groundwater sample collected from well MW5 and low levels were detected in samples collected from wells MW 1 and MW4 No gasoline constituents were detected in the sample collected from well MW3 Well MW5 contained TPHg at a concentration of 34,000 parts per billion (ppb), benzene at 3,700 ppb, toluene at 1,900 ppb, ethylbenzene at 970 ppb, and xylenes at 5,500 ppb Well MW1 contained TPHg at a concentration of 96 ppb, benzene at 1 6 ppb, and ethylbenzene at 2 8 ppb No toluene or xylenes were detected in well MW1 Well MW4 contained benzene at 0 8 ppb, toluene at 1 0 ppb, and xylenes at 1 4 ppb No TPHg or ethylbenzene were detected in well MW4 No TPHg or BTEX were detected in well MW3 Analytical results are summarized in Table 3 Laboratory data sheets and chain of custody documentation are included in Attachment C Figure 3 presents a benzene isoconcentration map from the most recent analytical results Attachment D contains graphical representations of TPHg and benzene concentrations over time in site wells G VaWGROUNDMKNOWLES HAMIREP0RTSIQMR11QM2002 doc