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Geolog£eal 7-eek1da kc Page 5 ' Groundwater Momtormg Report Project No 723 2 December 17,2002 ' 3.0 CONCLUSIONS & RECOMMENDATIONS ' Conclusions 1 Groundwater flow trends to the northe east The southerly flow direction recorded on December 4, 2000, appears to b anomalous 2 It is noted that the groundwater elevation exceeded the level of the well screens 3 High levels of BTEX and TPH-G are present in the groundwater of all six water table monitoring wells Low concentrations of BTEX and TPH-G are present in both of the deeper wells Generally, most of the wells show stable levels of contaminant concentrations over time 4 The groundwater contaminant plume is not defined vertically or laterally However, the decreasing concentration of contaminants in MW-201 suggests that this well may define the vertical edge of the plume in this location 5 Oxidation-Reduction Potential and Dissolved Oxygen measurements (Table 4) shows that all eight wells are screened in areas of the groundwater plume that are affected by the biodegradation reactions occurring within the plume The highly negative ORP values and the low DO content indicates that the wells are within the halo of reaction depleted water caused by biodegradation of the contaminants This suggests that the contaminant plume is stable and that natural attenuation processes are near a stand still, which corroborates well with the laboratory data Recommendations 1 GTI has submitted our July 27, 2002 "Additional Site Characterization Work Plan" with subsequent addendums The San Joaquin County PHS/EHD has approved the installation of three multi-chamber wells and these will be installed pending USTCFP cost pre-approval 2 Continue quarterly groundwater monitoring, with the next monitoring event scheduled ' in December 2002 4.0 LIMITATIONS This report was prepared in accordance with the accepted standards and practices of the field of environmental geology, groundwater hydrology and good business practices It should be recognized that definition and evaluation of environmental conditions is a difficult and inexact science Judgments leading to conclusions and recommendations are generally made with an incomplete knowledge of the site-specific conditions present