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13 September 2001 <br /> • AGE-NC Project No. 9 8-045 0 <br /> Page 4 of 6 <br />' Based on a southerly to south-southwesterly flow direction within the area contained by the six <br /> monitoring wells, wells MW-5 and BMW-2 are down-gradient from the former dispenser system <br /> and the former UST area. <br />' Table 1 shows the screen intervals for monitoring wells BMW-3, BMW-4 and BMW-5 and the <br /> assumed screen intervals for monitoring wells BMW-1 and BMW-2. The analytical results obtained <br /> are believed to be representative of the dissolved hydrocarbon concentrations in the shallow ground <br /> water at the site, as the wells are screened across the ground water table. <br />' 3.2. LABORATORY RESULTS OF GROUND WATER SAMPLES <br /> ' TPH-g was detected in four of the six samples collected at the site. TPH was detected at <br /> concentrations ranging from 120 micrograms per liter (�zg/l) in sample BMW-2 to 13,000 µg/l in <br /> sample BMW-4 (former UST area). <br /> TPH-d concentrations were detected in two of the samples at concentrations of 620 4g/1 in sample <br /> '• MW-5 and 6,300µg/1 in sample BMW-4. <br /> Benzene was detected in three samples BMW-1,BMW-2, and MW-5,at concentrations of 0.66µg/1 <br /> ' 3.4 µg/1 and 0.95 4g/l, respectively. The remaining BTEX compounds were detected at various <br /> concentrations with the highest concentrations occurring in MW-5 (120 µg/1 of ethyl benzene). <br /> ' MTBE was detected in samples BMW-2 and MW-5 by EPA method 8260 Modified at <br /> concentrations of 72 4g/1 and 330 4g/1, respectively. TBA was detected in samples BMW-2 and <br /> MW-5 by EPA method 8260 Modified at concentrations of 13 µg/1 and 90,ug/l, respectively. <br /> iThe laboratory report(MCAT Laboratory I.D.No. 69325 to 69330), Quality Assurance and Quality <br /> Control Data(QA/QC) and chain-of-custody forms are presented in Appendix B. The results of the <br /> ' analyses are summarized in Tables 2 and 3. <br /> ' 3.3. SOIL-VAPOR EXTRACTION <br /> The SVE unit operated at varying rates during the observation period. The duration of operation was <br /> recorde&with-an hour meter and recorded on-field logs. Extraction flow rates°were calculate&to <br /> range from 120 to approximately 150 cf n. An induced vacuum of approximately 25 to 50 inches of <br /> water was measured in the piping between the blower and extraction wells. <br /> Utilizing a PID,hydrocarbon concentrations were measured in the International System of Units(SI) <br /> ' of parts per million(ppm)at regular intervals at the SVE inlet,however a general concentration trend <br /> Advanced GeoEnvironmental,Inc. <br />