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1 ' I i August 1997 AGE-NC Project No 95-0173 ' Page 8 of 10 ' wells MW-1 through MW-4, MW-6 and MW-9 The highest concentrations were reported from B-3 at 28,000 ppb, while the lowest concentrations were reported from MW-9 at 6 9 ppb ' MTBE was not detected in any ground water samples submitted for laboratory analysis The analytical results from grab ground water samples are summarized in Table 2 The analytical results from quarterly ground water samples are summarized in Table 5 The laboratory reports (Castle Analytical Laboratory Reference No 975 and I 193) and chain-of-custody forms are included in Appendix H. ' 3 4 QUARTERLY RELATIVE GROUND WATER ELEVATION AND GRADIENT ' On 17 July 1997, the depths to ground water in wells MW-I through MW-9 ranged between 29 35 and 32 03 feet bsg Between April and July 1997, general ground water elevation at the site decreased an average of 0 41 feet Relative ground water elevations as measured on 17 Jul 1997 are depicted i > y p n Figure 12 In July 1997, the general ground water gradient at the site was calculated to be approximately 0 004 ft/ft or ' approximately 23 feet per mile and directed in a northeastward direction Between April and July 1997, the general ground water flow direction rotated from the northwest towards the northeast I 40 CONCLUSIONS/SUMMARY Based on the results of soil probe boring activities in December 1996, and the well installation and ground water monitoring activities performed in July 1997, AGE offers the following conclusions for consideration • Field observations and laboratory data indicate that petroleum hydrocarbon-impacted soil was encountered at depths between 20 and 40 feet bsg from VW-I and VW-2, at depths between 25 and 40-feet bsg from MW-6 and B-3, at depths between 30 and 40-feet bsg from B-6, at 30-feet bsg from B-4 Elevated concentrations of petroleum hydrocarbons were noted in the northern end of the former UST area, e g in B-2 and VW-2, at depths between 15 and 35 feet bsg • Results of the bioremediation analysis indicated that the physicochemical conditions at the site are inadequate to support microbial growth and bioremedial activity The analysis indicated that a degree of biotoxicity to the microbes may be present at the site, possibly due to agents such as heavy metals in the soil or to excessive concentrations of gasoline • Between April and July 1997, the general ground water flow direction rotated from the Inorthwest towards the northeast Ground water monitoring wells MW-3, MW-4, MW-5 and