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29 August 1996 <br /> AGE-NC-95-0101 <br /> Page 2 of 3 <br /> aromatic hydrocarbons (benzene,toluene ethylbenzene and xylenes, BTE&X) and methyl tert-butyl <br /> ether(MTBE) in accordance with EPA methods GCFID/5030 and 602, respectively <br /> 3.0. FINDINGS <br /> 3 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 fanged from 29 45 <br /> feet in MW-6 to 30 39 feet in MW-4 Ground water has risen an average of 105 feet since the April <br /> 1996 monitoring event As in previous quarters, the ground water elevation in MW-5 was <br /> anomalously low The cause of this anomaly is not currently understood, and water is not extracted <br /> from this well <br /> The ground water flow direction this quarter was generally toward the south at a gradient of <br /> approximately 0 007 ft/ft, but the gradient and flow direction were locally variable over the site July <br /> 1996 ground water elevation contours are illustrated on Figure 3 <br /> 32 LABORATORY ANALYSIS OF WATER SAMPLES <br /> TPH-g was detected in samples collected from MW-2 and MW-6 at concentrations of 230 ,ug/l <br /> (micrograms per liter, equivalent to parts per billion,ppb) and 57 ppb, respectively Benzene,toluene <br /> ethylbenzene and xylenes were detected in MW-2 at concentrations of 4 1 ppb, 5 0 ppb, 12 ppb and <br /> 48 ppb,respectively Toluene and xylenes were detected in MW-6 at concentrations of 0 68 ppb and <br /> 3 8 ppb, respectively MTBE was not detected in samples collected at the site Other petroleum <br /> hydrocarbons were not detected in samples collected during the July 1996 monitoring event The <br /> analytical results are summarized on Table 2 The laboratory report (MAI sample Nos 66633 to <br /> 66638) and chain-of-custody form are included in Appendix B <br /> 4 0. CONCLUSIONS & RECOMMENDATIONS <br /> Low concentrations of petroleum hydrocarbons were detected in two of the ground water monitoring <br /> wells sampled during the current monitoring event Low concentrations of petroleum hydrocarbons <br /> have been detected intermittently at the site over the last five years, with a maximum concentration <br /> of 230 ppb <br />