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20 March 1996 <br /> AGE-NC Project No 95-0130 <br /> Page 9 of 23 <br /> and labeling Each sample was logged on a chain-of-custody form and transported in a chilled <br /> container to Alpha Analytical Laboratories Inc (AAL), a California State-certified laboratory for <br /> analysis of TPH-g and BTE&X in accordance with EPA methods 5030/8015, and 602/8020, <br /> respectively <br /> 52 ANALYTICAL RESULTS OF GROUND WATER SAMPLES <br /> TPH-g was detected in groundwater samples from MW-2, MW-3 and MW-5 at concentrations of <br /> 180 µg/1 (micrograms per liter, approximately equivalent to parts per billion ppb), 3600 ppb, and <br /> 23000 ppb, respectively Benzene was detected from MWA through MW-3, and MW-5 at <br /> concentrations of 1 1 ppb, 5 1 ppb, 500 ppb, and 2800 ppb, respectively Toluene was detected from <br /> MW-2, MW-3, and MW-5 at concentrations of 0 49 ppb, 2 1 ppb, and 88 ppb, respectively Ethyl <br /> benzene was detected from MW-3 and MW-5 at concentrations of 290 ppb and 1500 ppb, <br /> respectively Xylene was detected from MW-3 and MW-5 at concentrations of 7 1 ppb and 1700 ppb, <br /> respectively The analytical results of all groundwater samples are summarized in Table 4 The <br /> laboratory reports and chains-of-custody are included in Appendix F <br /> 5 3 GROUND WATER CONDITIONS <br /> The relative elevation of ground water on 29 January 1996 is depicted in Figure 11 Between April <br /> 1995 and January 1996, ground water elevations rose approximately 3 11 feet in MW-1, 2 90 feet <br /> in MW-2, and 3 10 feet in MW-3 <br /> In January 1996, the ground water gradient at the site was calculated to be 0 0057 ft/ft <br /> (approximately 30 feet per mile) directed S 51' E In April 1995, the gradient was calculated to be <br /> 0 0016 ft/ft(approximately 8 feet per mile)directed S 60°E Between April 1995, and January 1996, <br /> ground water flow direction beneath the site rotated approximately 9° from the southeast toward the <br /> north <br /> 6.0. REMEDIATION OF HYDROCARBON-IMPACTED SOIL <br />! 61 SOIL VAPOR EXTRACTION <br /> Soil vapor extraction (SVE) is a well accepted method of treatment that has been used successfully <br /> at numerous sites with an excellent rate of success The method is most effective on volatile <br /> hydrocarbons in permeable soil <br />