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' 03 October 2001 • AGE-NC Project No. 95-0100 Page 6 of 6 4.0. SUMMARY AND CONCLUSIONS ' Based on the findings of this and previous investigations,AGE concludes the following: • TPH-g, BTEX and MTBE were not detected at or above laboratory reporting limits in selected soil samples collected from the borings for monitoring wells MW-4, MW-5 and MW-6 • The ground water flow direction was toward the northwest during the July 2001 sampling event.The ground water elevation decreased approximately 0.39 feet between the May 2001 ' and July 2001 monitoring events. • MTBE was detected in samples from monitoring wells MW-1,MW-3,MW-4 and MW-6 at ' concentrations as high as 150 µg11. • The MTBE concentrations exceeded the State of California maximum contaminant level (MCL) of 13 �ig/l in the water samples collected from wells MW-1 and MW-3. • TPH-g and BTEX compounds were detected in the water sample collected from well MW-4 during the 03 July 2001 sampling event. Monitoring well MW-4 was re-sampled on 16 July ' • 2001 to:confirm the results of the 03 July sampling event. TPH-g and BTEX compounds were not detected at or above laboratory reporting limits in the water sample collected from well MW-4 on 16 July 2001. ' The lateral extent of MTBE-impacted ground water has been fairly well defined. ' 5.0. RECOMMENDATIONS ' Based on the results of this investigation,AGE recommends that quarterly monitoring be continued. The next quarterly monitoring and sampling event should be conducted in October 2001. 'r A work plan to abandon domestic well DW-1 has recently been approved by San Joaquin County PHS-EHD. AGE anticipates the work will be performed during the fourth quarter of 2001. 1 6.0. LIMITATIONS Our professional services were performed using that degree of care and skill ordinarily exercised by environmental consultants practicing in this or similar localities. The findings were based mainly upon analytical results provided by an independent laboratory. Evaluations of the geologic/hydrogeologic conditions at the site for the purpose of this investigation were made from a limited number of available datapoints(i.e.soil and ground water samples from monitoring wells), ' and subsurface conditions may vary away from these data poiiits. No other warranty, expressed or implied, is made as to the professional recommendations contained in this report. Advanced GeoEMironmental,Inc,