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05 ,Pune 2003 <br /> AGE-NC Prod ect No 99-0637 <br /> Page 6 of 7 <br />' 4.0. SUMMARY AND CONCLUSIONS <br />' The following conclusions were drawn from the results of this investigation <br /> • Brown to tan fine sand with silt was encountered from surface grade to approximately 15 feet <br /> bsg In boring MW 10, to approximately 20 feet bsg In boring MW8 and to approximately 25 <br />' feet bsg in boring MW9 Dark brown to gray, silty clay was encountered at all other depths <br /> • MTBE was detected in the saturated soil samples collected from 25 feet bsg In boring MW9 <br />' and from 28 feet bsg In boring MW10 at low concentrations of 0 064 mg/kg and 0 048 <br /> mg/kg,respectively No other analytes were detected at or above laboratory reporting limits <br /> in the soil samples <br />' 0 The ground water elevations ranged from 15 83 feet to 17 53 feet above MSL Ground water <br /> flow was inferred to be ranging between a northwesterly flow direction on the east side of <br />' the site to a northeasterly direction on the west side of the site, the average ground water <br /> gradient was 0 005 feet/feet <br /> . e TPH-g, TPH-d,BTEX and fuel additives excluding MTBE,were not detected in any of the <br />' ground water samples collected from the site <br /> • MTBE was detected in the ground water samples collected from wells MW 1,MW2, MW4, <br />' MW5 MW6, MW9 and MW10 at concentrations ranging from 12 µg/l in well MW10 to <br /> 2,400 µg/1 In well MW 5 The highest concentrations of MTBE occurred in monitoring wells <br /> MW4 and MWS, which are located down-gradient of the UST area <br />' IP The lateral and vertical extent of impacted soil and vertical extent of impacted ground water <br /> has been defined at the site by previous investigations <br />' a The lateral extent of impacted ground water has only been defined to the east and south of <br /> the UST area However, low concentrations were encountered toward the north and west of <br /> the UST area, at wells MWl, MW2, MW9 and MW10 (1 2 µg/1 to 10 µg/1) An <br />' Iso-concentration map depicting the approximate distribution of dissolved MTBE is <br /> presented in Figure 6 <br /> 1 <br /> 5.0. RECOMMENDATIONS <br />' Based on the findings of this investigation, AGE recommends <br /> • Continuation of the quarterly ground water monitoring program The next monitoring event <br /> . should be performed in May 2003 <br /> 1 Advanced GeoEnvironmental,Inc <br />