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30 June 1995 AGE-NC-95-0101 Page 5 of 6 4 3 RELATIVE GROUND WATER ELEVATION AND GRADIENT The relative elevation of ground water in each well was calculated by subtracting the depth to water from the surveyed casing elevation (Table 2) All wells were surveyed relative to MW-3, which was assigned an arbitrary elevation of 100 feet The relative ground water elevation ranges from 25 30 feet in MW-6 to 26 09 feet in MW4 Ground water has risen an average of 0 53 feet since the November 1994 monitoring However, a greater rise in ground water was observed in MW-5 (2 08 feet) Monitoring wells MW-5 and MW-6 continue to show a lower ground water elevation An explanation for this anomaly is not clear Figure 3 is a ground water contour map drawn without using the data from MW-5 The gradient averages approximately 0 006 ft/ft The flow direction vanes from south at the north end of the site to southwest at the west side of the site This gradient is sirrular to previous gradients 4 4 LABORATORY EVIDENCE OF HYDROCARBON-IMPACTED GROUND WATER TPH-g was detected in the grab ground water sample from boring B9 at 300 gg/l (parts per billion ppb),BTE&X were detected at concentrations of 17 ppb, 4 0 ppb, 2 1 ppb and 28 ppb, respectively Xylenes were detected in the grab groundwater sample from boring B10 at 0 83 ppb No TPH, benzene, toluene or ethyl benzene were detected in the ground water sample from boring B 10 No petroleum hydrocarbons were detected in samples collected from monitoring wells at the site on 8 May 1995 The analytical results are summarized on Table 3 The laboratory report and chain-of- custody are included in Appendix B 5.0. CONCLUSIONS & RECOMMENDATIONS ' 5 1 HYDROCARBON-FVIPACTED SOIL TPH-g was detected in boring B9 at a depth of 35 feet However, only xylenes were detected at a depth of 45 feet No hydrocarbons were detected in any other soil samples from bonngs B9 or B 10 I Impacted soil in the area of MW-2 appears to limited to a narrow zone between 35 and 45 feet A limited vapor extraction test performed at the site by GeoAudit indicated that vapor extraction may be viable alternative for remediation of contaminated soil between MW-2 and VW-1 However, prior ' to initiation of any soil remediation at the site, we recommend preparation of a fate and transport model using the American Petroleum Institute's SESOIL program (or similiar) to determine if remediation at the site is necessary The results of this modeling should be sub rutted with the next