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' Mr Harlin Knoll Page 2 of 3 1 Monitoring wells MW1, MW4 and MW5 were purged a minimum of three well casing volumes of ' water and sampled on November 9, 2001 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 ' uses using a solution of laboratory-grade detergent, then double-rinsed in separate containers of clean rinse water ' Groundwater samples were collected using a dedicated, single-use, disposal bailer after the physical parameters stabilized The samples were decanted into preserved 40-m1 glass bottles and placed in an ice chest cooled to a temperature of at approximately 4°C The samples were transported to Argon Laboratories (ELAP 42359) under chain of custody protocol The samples were analyzed for the presence of 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 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 the sample collected from well MW l No gasoline constituents were detected in the sample collected from well MW4 Well MW5 contained TPHg at a concentration of 24,000 parts per billion (ppb), benzene at 2,700 ppb, toluene at 1,000 ppb, ethylbenzene at 330 ppb, and xylenes at 2,300 ppb Well MWl contained TPHg at a concentration of 560 ppb, benzene at 7 3 ppb, ethylbenzene at 27 ppb, and xylenes at 12 ppb No toluene was detected in well MW 1 Analytical results are summarized in Table 3 Laboratory data sheets and chain of custody documentation are included in Attachment 1 B Figure 3 presents a benzene isoconcentration map from the most recent analytical results Attachment C contains graphical representations of TPHg and benzene concentrations over time ' in site wells ' CONCLUSIONS AND RECOMMENDATIONS • Concentrations of dissolved TPHg and BTEX in wells MW 1 and MW5 have been gradually declining since their recorded highs BTEX constituents in well MW5 have declined by 91- 97% since December 1996 Contaminant concentrations in well MW 1 have decreased more than 82% from the recorded highs in that well e The consistently low levels of petroleum hydrocarbon constituents detected in well MW 1 coupled with the absence of contaminants in wells MW2 and MW4 suggest that well MW 1 is located at the approximate southeastern (downgradient) extent of the dissolved contaminant • plume 1 Knowles hamlreports/4gm2001 dm