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v t3 Mr Michael Infurna Page 2 Prior to sampling, monitoring wells MW1 through MW5 were purged a minimum of three well casing volumes During the purging process, temperature, pH and electrical conductivity parameters were measured Samples were collected after parameter stabilization, and appropriate water level recovery Purge water was contained in properly labeled DOT-approved 55-gallon drums The drums are currently being stored onsite Purge logs are included in Attachment A Groundwater samples were delivered under chain of custody protocol to Argon Laboratories (ELAP #2359) Analysis consisted of TPHg and TPHd using modified EPA method 801513, gasoline oxygenate additives using EPA method 8260B, and BTEX using EPA method 8021B Groundwater Analytical Results BTEX, EDB and 1,2 DCA were not detected in any site wells TPHg, TPHd and gasoline oxygenates were not detected in wells MW1, MW2, MW4 and MW5 In well MW3, TPHg was detected at a concentration of 630 parts per billion (ppb) TPHd was detected at a concentration of 14,000 ppb Methyl-tent-butyl ether (MTBE) was detected at a concentration of 930 ppb Analytical results are summarized in Table 2 Attachment B contains laboratory reports and chain of custody documentation Graphs of TPHg, TPHd and MTBE concentrations over time in MW3 are included in Attachment C Summary © Groundwater levels at the site fell since the previous round of sampling These are the lowest water table elevations measured since the monitoring wells were installed in November 1999 The average groundwater gradient across the site was 0 002 — 0 003 ft/ft Groundwater flowed predominantly in a northeasterly direction This is the fourth consecutive quarterly monitoring event in which flow was toward the northeast • BTEX, EDB and 1,2 DCA were not detected above laboratory method detection limits (MDLs) in any site well Gasoline oxygenates, TPHg and TPHd concentrations were less than MDLs in wells MW1, MW2, MW4 and MW5 • Relative to the previous sampling event, the concentration of TPHd in well MW3 increased an order of magnitude while the levels of TPHg and MTBE increased by less than 20% Conclusions The contaminant plume is localized in the immediate vicinity of well MW3, and is of very limited extent Although concentrations spikes can occur from time to time, the cumulative data indicate that the plume is not migrating, and dissolved contaminant concentrations are stable to decreasing %%GZA_FSIVOL I\DATAIGROUNDZC\W00LS$Y CHTIQMRU00314QM2003 doc