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Mr Harlin Knoll <br /> Page 2 of 3 <br /> Monitoring wells MWI through MW4 were purged of at least three well casing volumes of water <br /> prior to sampling Temperature, pH, and electrical conductivity were measured during the purging <br /> process Samples were collected after the physical parameters had stabilized and water levels had <br /> recovered to at least 80% of pre-purged levels Purged groundwater was contained in appropriately <br /> labeled DOT-approved 55-gallon drums The drums are currently being stored onsite pending <br /> disposal Purge logs are included in Attachment A <br /> Groundwater samples were delivered under chain of custody protocol to Argon Laboratories <br /> (FLAP #2359) Samples were analyzed for the presence of TPHg using EPA method 8015M, <br /> BTEX using EPA method 8020, and oxygenated gasoline additives, 1,2-DCA, and EDB using <br /> EPA method 8260B <br /> i <br /> GROUNDWATER ANALYTICAL RESULTS <br /> TPHg and BTEX continue to be less than laboratory method detection limits (MDL) in all site <br /> wells Methyl tent butyl ether (MTBE) was the only chemical of concern detected at the site <br /> MTBE was detected in wells MW1, MW3 and MW4 at 6 8 parts per billion (ppb), 290 ppb <br /> and 3 8 parts ppb, respectively No MTBE has been detected in well MW2 since sampling <br /> began at the site Analytical results are summarized in Table 2 MTBE concentrations over <br /> time in site wells are illustrated on Figure 3 Attachment B contains laboratory reports and <br /> chain of custody documentation for samples collected during the reporting period <br /> SUMMARY AND CONCLUSIONS <br /> • Groundwater levels at the site fell an average of 0 69 feet since the last round of sampling The <br /> groundwater gradient was approximately 16 feet per mile toward the southwest <br /> • MTBE was the only constituent of concern detected at the site during this round of sampling <br /> MTBE concentrations in site wells decreased from the previous sampling event No <br /> constituents of concern were detected in well MW2 <br /> • No TPHg or BTEX has been detected in any site wells since sampling began at the site <br /> • MTBE concentrations in site wells in June 2002 were below the Primary Maximum <br /> Contaminant Level (MCL) of 13 ppb in wells MW1, MW2, and MW4 MTBE remained <br /> above the MCL only in well MW3 (290 ppb) <br /> RECONEAENDATIONS <br /> Based upon historical site data, Ground Zero makes the following recommendations <br /> Discontinue analysis of TPHg and BTEX in all site wells Groundwater samples collected in <br /> 0 1Data\QROUNDZE\Barnyard-Manscr\Reports\QMR12QM2002 doe <br />