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11 May 1998 <br /> AGE-NC Project No 97-0312 <br /> Page 4 of 5 <br /> then used to backfill the excavation to approximately one foot bsg Soil with concentrations of TPH- <br /> g greater than 100 ppm or TPH-d greater than 1,000 ppm were transported for disposal Soil with <br /> concentrations of TPH-g and TPH-d less than 100 ppm and 1,000 ppm, respectively, were used as <br /> backfill material <br /> 4,0. FINDINGS <br /> 41 GROUND WATER ELEVATION AND GRADIENT <br /> The elevation of ground water in each well was calculated by subtracting the depth to water from <br /> the surveyed casing elevation (Table 1) The ground water elevation Increased an average of 11 03 <br /> feet since the December 1997 monitoring event Ground water was approximately 30 feet above the <br /> screened interval In UST-1, ten feet above the screened interval in UST-2, UST-3 and UST-4 <br /> approximately one foot above the screened interval In UST-5 The ground water flow direction was <br /> inferred to be northeasterly with a gradient of 0 004 ft/ft The flow direction is similar to previous <br /> monitoring events Figure 4 - Ground Water Elevation depicts the contours for March 1998 <br /> 42 ANALYTICAL RESULTS OF GROUND WATER SAMPLES <br /> TPH-g was detected in the sample collected from monitoring well UST-5 at a concentration of 2,500 <br /> parts per billion(ppb,reported as micrograms per liter) Benzene, toluene, ethylbenzene and \ylenes <br /> were detected in this sample at concentrations of 840 ppb, 10 ppb, 12 ppb and 19 ppb, respectively <br /> Benzene was detected In the sample collected from UST-1 at a concentration of 1 5 ppb TPH-d was <br /> detected in UST-1, UST-2, UST-4 and UST-5 at concentrations of 520 ppb, 130 ppb, 120 ppb and <br /> 1,500 ppb,respectively Other petroleum hydrocarbons were not detected in samples collected at the <br /> site <br /> MTBE was detected in UST-5 at a concentration of 14 ppb However, the presence of MTBE was <br /> not confirmed by EPA Method 8260 1,2-Dschloroethane (DCA) was detected in the sample <br /> collected from UST-5 at a concentration of 810 ppb Other volatile organic compounds including <br /> oxygenating compounds were not detected in ground water samples from the site The analytical <br /> results are summarized on Tables 2 and 3 The laboratory report(MAI sample Nos 86673 - 86677) <br /> and chain-of-custody form are included In Appendix B <br /> 43 SOIL COMPACTION TESTS <br /> Compaction of 93 8 percent and 92 8 percent were calculated for soil at a depth of 7 feet bsg A copy <br /> Advanced GeoEnvironmeats 1,Inc <br /> J <br />