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17 January 2005 AGE-NC Project No 95-0103 Page 8 of 9 detected in each extraction well are noticeably less than 2003 MTBE concentrations (Table 4) • Based on the amount of ground water processed and laboratory analytical results, approximately 0 57 lbs of benzene and 32 lbs of TPH-g were removed from the extracted ground,water (Appendix D) Cumulative totals of 6 46 lbs of benzene and 178 7 lbs of TPH-g are estimated to have been extracted since ground water treatment began on 02 April ' 2002 • The average ground water level was approximately 14 9 feet below the top of the casing, a ground water rise of approximately 0 8 feet since the monitoring event in December 2003 The ground water flow direction was radially inward toward the area of the extraction wells ' • With the exception of well MW-1, the ground water table was within the screened interval of wells MW-5 and MW-6 and within one foot above the top of the screened interval of wells MW-2 through MW-4, these wells should yield samples representative of shallow ground water conditions The water table was approximately 2 feet above the screened interval of well MW-1,water samples collected from well MW-1 may not be representative of shallow ground water conditions • With the exception of wells MW-4 and VE-5, located on the eastern edge of the site, the TPH-g and BTEX concentrations continue to decline or remain stable in the monitoring well network, BTEX compounds were detected only in well MW-4 in fourth quarter 2004 However,TPH-g increased significantly in wells MW-4 and VE-5 during fourth quarter 2004 relative to fourth quarter 2003 (MW-4) and second quarter 2003 (VE-5), this increase in TPH-g concentrations may be attributed to capture and drawing-in of the northeastern edge of the dissolved TPH-g plume • MTBE was detected in wells MW-4 and VE-1/AS at 9 5 µg11 and 4 9 µg/l,respectively The ' MTBE concentration in well MW-4 slightly exceeds California's secondary contaminant level of 5 0 µg/1 for drinking water 5.0. RECOMMENDATIONS TPH-g and BTEX concentrations have decreased in the extraction well samples over the remediation period, trend analyses indicate that ground water extraction is capturing and removing dissolved petroleum hydrocarbons Based upon the results of the fourth quarter 2004 ground water monitoring event,AGE recommends • Continued quarterly ground water monitoring at the site as required by California Code of Regulations ' Advanced GeoEnvironmental,Inc