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n <br /> ATC Associates Inc <br /> GVV <br /> 1117 Lone Palm Avenue, Suite B <br /> RTC Modesto, California 95351 <br /> 209-579-2221 <br /> ASSOCIATES I NC fax 209-579-2225 <br /> temperature were measured in groundwater purged from each monitoring well and recorded A <br /> minimum of three well casing volumes was purged from each well prior to sampling The wells <br /> were allowed to recover and a sample was collected from each well using a disposable bailer <br /> Groundwater well purge and sample logs are contained in Attachment 1 <br /> The groundwater samples collected from the wells were submitted to State certified Argon <br /> Laboratories (ELAP Cert No 2359) for chemical analyses of TPHg, total petroleum <br /> hydrocarbons quantified as diesel (TPHd), and total petroleum hydrocarbons quantified as <br /> kerosene (TPHk) utilizing EPA Method 8015B, BTEX utilizing EPA Method 8021B, and <br /> oxygenate fuel additives including methyl tert-butyl ether (MTBE) utilizing EPA method 8260B <br /> ANALYTICAL RESULTS <br /> Petroleum hydrocarbons were only detected in the groundwater samples collected from MW2 <br /> Benzene was detected in the groundwater sample collected from MW2 at a concentration of 12 <br /> gg/L TPHg was detected in the groundwater sample collected from MW2 at a concentration of <br /> 78 µg/L <br /> MTBE was not detected in any of the groundwater samples collected from MW 1 through MW7 <br /> at or above the laboratory detection limits Groundwater samples collected from wells MW 1, <br /> MW3, MW4, MW5, MW6, and MW7 did not contain concentrations of TPHg, TPHd, TPHk, <br /> BTEX constituents, or fuel oxygenates at or above the laboratory reporting limits Analytical <br /> results for groundwater samples are contained in Table 2 Laboratory data sheets and chain-of- <br /> custody documentation are contained in Attachment 2 <br /> CONCLUSIONS <br /> The concentration of petroleum hydrocarbons in groundwater samples collected from MW2 are <br /> within the historical range as established by previous sampling events and have generally <br /> decreased over time Concentrations of petroleum hydrocarbons remained below laboratory <br /> reporting limits in samples collected from MW1, MW3, MW4, MW5, MW6, and MW7 TPHk <br /> has not been detected in samples collected from wells MW1, MW2, and MW3 since at least <br /> 2000 TPHd has not been detected in samples collected from wells MW1 through MW4 since at <br /> least March 2001 TPHk has never been detected in samples collected from wells MW4 through <br /> MW7 THPd has never been detected in samples collected from wells MW5 through MW7 The <br /> lateral extent of the petroleum hydrocarbon plume in groundwater appears to be receding <br /> S\6257712QR 2004 doc <br />