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{ Mr Mike Infurna Page 2 event was abnormally steep Typically, the gradient at the site is flat While water levels measured in the deeper wells at the site fell over 6 feet since June, the water levels measured in wells MW3 and MW4 fell only 4 to 5 feet Also, water levels in wells MW3 and MW4 did not recovery after purging We believe it is likely that the water measured in these wells was perched in the well casing A potentiometric surface map generated using the September 18, 2002 monitoring data is shown on Figure 2 Groundwater monitoring data are summarized in Table 1 Monitoring data sheets are included in Attachment A On September 18, 2002, wells MWI, MW3, MW4 and U-Haul well MW7 were purged MW1 and U- Haul well MW7 were purged of at least three well casing volumes prior to sample collection During the purging process, temperature, pH and electrical conductivity parameters were measured Groundwater samples were collected after physical parameter stabilization Subsequently the samples were placed in an ice chest refrigerated to a temperature of approximately 4°C Purgewater was contained in appropriately labeled DOT-approved 55-gallon drums Wells MW3 and MW4 went dry while being purged and water did not recharge into the wellbores Consequently, samples were not collected from MW3 and MW4 Purge logs are included in Attachment A Groundwater samples were delivered under chain of custody protocol to Argon Laboratories (ELAP #2359) Analysis consisted of gasoline oxygenate additives, 1,2-DCA and EDB using EPA method 8260, BTEX using EPA method 8020, and TPHg using modified EPA method 8015 GROUNDWATER ANALYTICAL RESULTS Gasoline oxygenate additives and EDB were not detected in the samples collected from monitoring wells MW1 and U-Haul MW7 Dissolved TPHg, BTEX and 1,2—DCA concentrations reported in well MW1 were relatively similar to those from the previous event In well U-Haul MW7, TPHg and benzene concentrations increased since the previous sampling event and 1,2—DCA was detected after being at non detectable levels during the previous event Analytical results are summarized in Table 2 Attachment B contains laboratory reports and chain of custody documentation SUMMARY • The apparent groundwater gradient at the site was significantly steeper than historical measurements, and groundwater appeared to flow in a west-southwesterly direction However, the gradient was calculated using water level measurements from wells MW3 and MW4, which we believe may not have been representative of actual conditions • Concentrations of TPHg, BTEX and 1,2-DCA in well MW1 were similar to those measured during previous sampling events In well U-Haul MW7, TPHg, BTEX and 1,2-DCA increased since the last event • ❑GZA_FS1SY501\Data\GROUNDZEVLARRYS\Repox%NQMR\2002\3QM2002 doc