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ASS O C I ATE S I N C .
<br /> towards the north. The average hydraulic gradient on July 2, 2003 was calculated to be 0.0009
<br /> or approximately 4.8 ft/mile. A summary of groundwater monitoring data is presented in Table
<br /> 1.
<br /> SAMPLING ACTIVITIES
<br /> On July 2, 2003, ATC personnel collected groundwater samples from monitoring wells MWI,
<br /> MW2, and MW3. The locations of the monitoring wells are shown on Figure 2. Prior to
<br /> collection of groundwater samples, the depth to water, pH, electrical conductivity, and
<br /> temperature were measured in the monitoring wells and recorded. A minimum volume of three
<br /> well casings was purged from each well prior to sampling. The wells were allowed to recover
<br /> and samples were collected from each well using a disposable bailer.
<br /> The groundwater matrix samples collected from each well were submitted to State-certified
<br /> Argon Laboratories (ELAP Cert. No. 2359) for chemical analysis of TPHg utilizing EPA method
<br /> 8015 modified, and BTEX and oxygenate fuel additives including MTBE utilizing EPA method
<br /> 8260. Groundwater well purge and sample logs are contained in Attachment 1.
<br /> ANALYTICAL RESULTS
<br /> . The groundwater analytical results measured at monitoring wells MWI, MW2, and MW3
<br /> showed detectable concentrations of TPHg, BTEX, MTBE, TBA, and 1,2-DCA.
<br /> The Maximum Contaminant Level (MCL) for benzene, I µg/L, was exceeded at monitoring
<br /> wells MW2 and MW3 which had detected concentrations of 8.2 and 2.1 µg/L, respectively. The
<br /> MCL for MTBE, 13 µg/L, was exceeded at MWI, MW2, and MW3, which had detected
<br /> concentrations of 30 µg/L, 52 pg/L, and 97 ug/L, respectively. The MCL for 1,2-DCA, 0.5
<br /> gg/L, was exceeded at monitoring wells MWI, MW2 and MW3, which had detected
<br /> concentrations of 43 µg/L, 38 µg/L, and 51 µg/L, respectively. An Action Level for TBA, 12
<br /> pg/L, was exceeded at wells MWI, MW2, and MW3 that had detected concentrations of 46
<br /> µg/L, 52 gg/L, and 36 µg/L, respectively.
<br /> CONCLUSIONS
<br /> Groundwater flow direction and gradient is consistent with previous sampling events. Water
<br /> table elevations have decreased since the April 2003 monitoring event. Groundwater analytical
<br /> results show a slight increase in concentrations, though most remained within historical
<br /> parameters as set by previous groundwater analytical results.
<br /> RECOMMENDATIONS
<br /> Based on the results of the third quarter 2003 monitoring event, we recommend continued
<br /> . quarterly groundwater monitoring with analysis of samples for TPHg, BTEX, and fuel
<br /> oxygenates.
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