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A S S Q C I A T E S I N C QUARTERLY GROUNDWATER MONITORING ACTIVITIES On September 11, 2003, ATC personnel collected groundwater samples from monitoring wells MW1 through MW10 and CW The locations of the monitoring wells are shown on Figure 2 Prior to collection of groundwater samples, the depth to water, pH, electrical conductivity, and temperature were measured in the monitoring wells and recorded A minimum of three well casing volumes was purged from each well prior to sampling The wells were allowed to recover and samples were collected from each well using dedicated disposable bailers After groundwater ' samples were collected, dissolved oxygen concentrations were measured in each well Groundwater well purge and sample logs are contained in Attachment 1 ' The groundwater samples collected from each well were submitted to State-certified Argon Laboratories, Inc (ELAP Cert No 2359) for chemical analyses of TPHg by EPA method 8015B, benzene, toluene, ethylbenzene, xylenes (BTEX) by EPA method 8021B, and methyl tertiary butyl ether (MTBE), ethyl tertiary butyl ether (ETBE), tertiary butyl alcohol (TBA), tertiary amyl ether (TAME), di-isopropyl ether (DIPE), 1,2-dichloroethane (1,2-DCA), and ethyl dibromide i (EDB) by EPA method 8260B Groundwater Analytical Results TPHg and/or BTEX constituents were detected at or above laboratory reported detection limits in the samples collected from wells MW 1, MW5, MW6, and MW7 The groundwater samples collected from wells MW2, MW5, MW6, MW7, MW9, and CW contained low concentrations of MTBE ranging from 1 9 parts per billion (ppb) to 12 ppb The groundwater samples collected from MW 1, MW3, MW4, MW8 and MW 10 did not contain detectable concentrations of MTBE, ' but the detection limits in the sample collected from MW I were elevated due to dilution factors None of the groundwater samples collected contained detectable concentrations of ETBE, TBA, TAME, DIPE, 1,2-DCA, or EDB The samples collected from MW2, MW4, MW9, MW 10, and ' CW contained no detectable concentrations of petroleum hydrocarbons other than low concentrations of MTBE The groundwater sample collected in September 2003 from MW3, located near the vapor extraction wells, contained a slightly lower concentration of MTBE than the sample collected in June 2003 Groundwater samples collected from MWI and MW7 contained slightly increased ' concentrations of TPHg and BTEX with respect to the samples collected from these wells in June 2003, but are within historical ranges Concentrations in the remaining wells generally were the same as those detected in June 2003 A summary of analytical results is presented in Table 1 1 Groundwater laboratory data sheets and chain-of-custody documentation are contained in Attachment 2 i w Iwordpro1625961quart1yl3gr-2003 doc 3