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15 September 1999 <br /> AGE-NC Project No 98-0592 <br /> Page 6 of 7 <br /> Utilizing EPA Method 8260, MTBE was detected in grab samples collected from B 1, B2, and B5 <br /> at concentrations of 160 ug/l, 7 4 ug/1, and 9 9 ug/l, respectively <br /> Analytical results of ground water grab samples are summarized in Table 5 Copies of the laboratory <br /> reports and chain-of-custody forms are presented in Appendix B <br /> 5 0 SUMMARY AND CONCLUSIONS <br /> Based upon data collected during the 10 and 11 June 1999 Preliminary Site Assessment, AGE <br /> concludes <br /> • Laboratory analysis of grab ground water samples indicate that the highest concentration of <br /> TPH-g is located beneath the former UST system in boring B 1 at a depth of approximately <br /> 45 feet bsg <br /> • BTEX compounds were detected in soil samples from boring B1 at depths as great as 40 feet <br /> . bsg and in grab ground water samples from B 1 and B2 <br /> • MTBE was detected in soil samples from borings B 1 and 132, and in grab ground water <br /> samples B1-W, 132-W, and 135-W The highest concentration of MTBE in ground water was <br /> detected beneath the UST system from boring BI Sample 135-W, which was located <br /> approximately 100 feet northeast of the former UST area, had a higher concentration of <br /> MTBE than the closer B2-W sample, which was located approximately 30 feet southwest of <br /> the UST area This data may validate the northeast ground water flow direction <br /> Additionally,the ground water data may illustrate an example of the relatively rapid mobility <br /> of MTBE, compared to other petroleum hydrocarbon constituents, through ground water <br /> 6 0 RECOMMENDATIONS <br /> Based on data collected during June 1999, AGE recommends <br /> • Further subsurface evaluation of the lateral extent of petroleum hydrocarbon impact to <br /> ground water, especially in the down-gradient direction, <br /> • Installation of ground water monitoring wells located as depicted in Figure 2, and <br /> • Quarterly ground water monitoring and sampling should be initiated at the site to better <br /> characterize and monitor the hydrocarbon impact to ground water and plume stability on the <br /> site <br /> Adiarced GeoEnN ironmcntal,Inc <br />