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Other that the event cited above,no anomalous or unexpected results were reported The concentration of TPHg at 1,700 µg/L in the groundwater sample collected from monitoring well BEI-MW3 during the ' most recent(November 15, 2001) monitoring event is the lowest ever reported during the several year period of groundwater momtonng The corresponding concentration of benzene at 61 pg/L is also the lowest ever reported for this compound and is consistent with the generally asymptotic trend During ' the August 1, 2001 monitoring event,the groundwater sample from monitoring well BEI-MW3 was also analyzed for the gasoline oxygenates by EPA Method 8260 None of the oxygenates were present above ' the laboratory detection levels The data that are most significant for assessing the achievement of the remediation program are the groundwater monitoring results presented in Table 7 For the four most severely impacted monitoring wells, Table 7 presents a comparison of the average TPHg and benzene concentrations for samples collected during the three morutoring events prior to the startup of the remediation program(in February ' 1998) with the average results for the three most recent monitoring events These results show near total elimination of total hydrocarbons in most of the previously impacted monitoring wells, and reductions of more than 95 percent to near 100 percent in the severely impacted monitoring wells BEI- ' MW3 and BEI-MW1 Reductions of benzene in these wells are 98 7% percent and more than 99 percent, respectively 2.2 Groundwater Elevations and Gradients A summary of the November 2001 and previous groundwater elevation measurements are presented on Table 3 Groundwater elevations for the August 1, 2001 and November 15, 2001 measurements are presented in Figures 4a and 4b,respectively Copies of the field purge/sampling worksheets are included as Appendix C 1 3.0 CONCLUSIONS AND RECOMMENDATION ' groundwater monitoring result reported herein confirm ATC's earlier assessment that the The recent gro g p ' small remaining levels of hydrocarbons at the site are continuing to biodegrade and present no perceivable environmental hazard In fact, we believe that the presence of the existing groundwater monitonng and extraction wells currently present more of an environmental risk than does the small ' remaining hydrocarbon concentrations detected in only one well Accordingly, ATC recommends immediate closure of the site with prompt destruction of these wells 1 Value Reclamation, Manteca, CA OVATC 2 ATC Project No 75999757501 January 9,2002