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27 June 2002 <br /> AGE-NC Project No. 98-0520 <br />' Page 7 of 8 ; <br /> TBA was detected by EPA Method 8260B in ground water samples from wells MW-2.and MW-3 <br />' at concentrations of 61 pg/l and•300 gg/l, respectively. <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 3.. A Map showing the lateral <br /> distribution of TPH-g and TBA is provided in Figure 10. Copies of the laboratory report (CTEL <br /> Project No. CT214-0112030) and chain-of-custody forms are in Appendix E. <br /> 4.0.. , SUMMARY AND CONCLUSIONS <br /> ' Based upon data collected from the site, AGE concludes: <br /> P • <br /> The general stratigraphy at the site, 'determined from soil borings, -consisted of three <br /> subsurface layers, an upper 20-foot sand layer overlying a 15-foot clayey to sandy silt layer, <br /> which in turn is apparently underlain by another sand layer to the maximum depth of <br /> investigation of 50 feet bsg. <br /> TPH-g (130 mg/kg), TPH-d (150 mg/kg) and TPH-mo (10 mg/kg) was detected in soil <br /> sample MW-9-20,.and TPH-g (15 mg/kg) was detected in soil sample MW-8-30. Various <br /> BTEX compounds except benzene were detected in soil samples MW-6-35, MW-8730 and <br /> MW-9-20 at a maximum concentration of 0.83 mg/kg ethylbenzenc, in the sample from " <br /> MW-9-20. <br /> • MTBE was detected in soil samples for the first time, at a concentration of 0.0075 mg/kg in <br /> 1 sample MW-9-25. <br /> • The high concentrations'of petroleum hydrocarbons,plus the detected presence of MTBE <br /> for the first time,in soil samples from boring MW-9 suggest that soil contaminants at MW-9 <br /> ' may have originated from a different source area. <br /> • Petroleum hydrocarbons were not detected in soil samples from deep well MW-6,nor at total <br /> ' depth in wells MW-8 through MW-10; the vertical extent of contaminated soil is defined. <br /> • Ground water elevations'at the site averaged approximately 16.1 feet relative to MSL on <br /> '05 December 2 00 1,an elevation drop of approximately 2 feet from the previous quarter.The <br /> ' net ground water flow was towards the northwest under an average gradient of 0.004 ft/ft., <br /> • TPH-g concentration increased by a factor of two in ground water samples from MW-1 <br /> ' through MW-5 from the previous quarter, <br /> ' Advanced GeoEnvironmental,Inc. ' <br />