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22 December 1995 <br /> AGE-NC Project No 95-0101 <br /> Page 4 of 5 <br /> 4.0. FINDINGS <br /> 4 1 RELATIVE GROUND WATER ELEVATION AND GRADIENT <br /> The relative elevation of ground water in each well was calculated by subtracting the depth to water <br /> from the surveyed casing elevation (Table 1) All wells were surveyed relative to MW-3, which was <br /> assigned an arbitrary elevation of 100 feet The relative ground water elevation ranges from 26 78 <br /> feet in MW-6 to 27 72 feet in MW-4 Ground water has risen an average of 1 51 feet since the May <br /> 1994 monitoring However, the elevation of ground water to monitoring wells MW-5 and Mur-6 has <br /> continued to drop Since no water extraction from these wells is conducted, this anomaly could not <br /> be explained <br /> Figure 3 depicts the ground water contour without using the data from MW-5 The gradient averages <br /> approximately 0 0054 ft/ft, which has remained relatively consistent throughout the monitoring <br /> period The ground water flow direction is slightly west of south <br /> 42 LABORATORY ANALYSIS OF WATER SAMPLES <br /> NoP etroleum hydrocarbons were detected in samples collected from monitoring wells on 10 August <br /> 1995 Toluene was detected at a concentration of 0 62 ppb in the composite sample collected from <br /> the purged water drums The analytical results are summarized on Table 2 The laboratory report and <br /> chain-of-custody form are included in Appendix B <br /> 5.0. CONCLUSIONS &c RECOMMENDATIONS <br /> 5 1 HYDROCARBON-IMPACTED SOIL <br /> Figure 4 depicts a north-south cross section showing the approximate extent of impacted soil near <br /> MW-2 and VW-1 Impacted soil appears to be limited to a narrow zone between 35 and 45 feet <br /> Vapor extraction may be viable alternative for remediation of contaminated soil between MW-2 and <br /> VW-1 Due to the small volume of impacted soil and low concentrations of hydrocarbons, vapor <br /> extraction could be performed using a relatively simple vapor extraction system with activated carbon <br /> filtration for vapor abatement for a cost effective remediation method <br /> 5 2 HYDROCARBON-IMPACTED GROUND WATER <br /> Petroleum hydrocarbons were detected in the grab ground water sample collected from boring 139, <br /> located approximately 15 feet northwest of MW-2 However, petroleum hydrocarbons were not <br />