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CIA' A S S O C I A T E S I N C that horizontal isotropic conditions prevail, groundwater in the uppermost aquifer beneath the site flowed in a north-northwest direction. The average hydraulic gradient on June 14, 2001 was calculated to be 0.002 ft/ft or about 11 feet/mile. The data indicates a groundwater gradient that is generally consistent with previous groundwater gradients observed at the site. A summary of groundwater monitoring data is presented in Table 1. Groundwater elevations are referenced to feet above mean sea level. Groundwater samples were collected from monitoring wells MW-1 through MW-6. Prior to collection of groundwater samples a minimum of three well casing volumes were purged. The depth-to-water, pH, electrical conductivity, and temperature were measured and allowed to stabilize before groundwater samples were collected. Samples were then collected from each well using disposable bailers. Purge water was contained in 55-gallon DOT approved drums. Purge water from monitoring wells MW-1 and MW-6 from the previous sampling event did not contain detectable concentrations of petroleum hydrocarbons and was discharged to the ground surface. Groundwater well purge and sample logs are provided in Appendix A. The groundwater samples collected from each well were submitted with Chain of Custody Record to State-certified Argon Laboratories Inc. (FLAP Cert. No. 2359). The samples were analyzed for TPHg by EPA method 8015; BTEX and MTBE by EPA method 8020. Groundwater analytical results are summarized in Table 2. The laboratory analytical reports are included in `.. Appendix B. RESULTS OF LABORATORY ANALYSES Results of the laboratory analysis of groundwater samples from the monitoring wells indicate the presence of petroleum hydrocarbons in groundwater samples from monitoring wells MW-2 and MW-3. No petroleum hydrocarbons were detected in monitoring wells MW-1, MW-4, MW-5, and MW-6. The analytical results are summarized in Table 2. CONCLUSIONS AND RECOMMENDATIONS Results of the most recent monitoring event indicate that the concentrations of petroleum hydrocarbons in the groundwater have generally remained the same or increased since the last monitoring event. The groundwater gradient direction has remained the same. Based on the results ATC recommends continued groundwater monitoring. ATC also recommends the evaluation of groundwater extraction as a remedial alternative for the site. Upon concurrence of this recommendation by PHS/EHD, ATC will prepare a workplan for performing a groundwater extraction pilot test. wA17861\repoAs\2gnv2001.dw 3