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14 December 2001 <br /> ,AGE-NC Project No. 98-0520 <br /> Page 3 of 4 <br /> 310 µg/1 and 370 µg/l, respectively-All concentrations of these analytes were below California's <br /> ' Maximum Contaminant Levels for drinking water. <br /> TBA was detected by EPA Method 8260B in ground water samples from MW-2 through"MW-5 at <br /> ' concentrations ranging from 30 µg11 in MW-4 to 170 µg/1 in MW-3. <br /> MTBE, EDB and 1,2-DCA were not detected at or above-laboratory reporting limits in the ground <br /> water samples collected. <br /> ' Analytical results of ground water samples are summarized on Table 2. The laboratory report(MAI <br /> Lab I.D. No. 77620 through 77624) and chain-of-custody forms are included in Appendix B.- <br /> 4.01 , <br /> .4.0 , SUMMARY AND CONCLUSIONS <br /> Based upon data collected from the site, AGE concludes: <br /> • Depth to ground water at the site averaged approximately 22.7 feet bsg on 10 September <br /> lie 2001. <br /> • On 10 September.2001 the ground water elevation at the site averaged approximately 14.04 <br /> ' feet above mean sea level,with a net flow towards the northwest under an average gradient <br /> of 0.0005 ft/ft. <br /> * TPH-g concentration decreased in ground water samples from MW-1 through MW-5 from <br /> ' the previous quarter monitoring. <br /> • TPH-g and various BTEX compounds were detected in all five ground water monitoring <br /> ' wells on-site. <br /> •" TBA was detected in four of the.five groundwater monitoring wells at concentrations as high <br /> ' as 170 µgd. <br /> ' 5.0. RECOMMENDATIONS <br /> Based upon data collected from the site, AGE recommends continued quarterly ground water <br /> monitoring. Four additional monitoring wells were installed on 30 and 31 October 2001; a fifth . <br /> monitoring well will be installed west of the site, pending City of Manteca approval. The next <br /> quarterly monitoring event is scheduled for 05 December 2001. <br /> y <br /> ' Advanced GeoEnvironmental,Inc. <br />