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13 December 1999 <br /> AGE-NC Project No. 98-0433 <br /> Page 10 of 13 <br /> of general microbial population. Hydrocarbon.concentrations may be high enough to stimulate the <br /> selective,bio degrader populations to accelerate natural attenuation. <br /> Under the present circumstances, natural attenuation of hydrocarbons in ground water by <br /> ' bioremediation is likely to occur on site with biogegraders present in the ground water. However, <br /> to demonstrate that continual bioremediation is occurring, additional bioenumeration analysis of <br /> ground water samples would need to be conducted. The laboratory report (A. Keith Kaufman <br /> ' [7imco]) and chain-of-custody form are included in Appendix F. <br /> 1 4.4. HYDROCARBON-IMPACTED GROUND WATER <br /> A total of five grab water.samples were collected on the site. Additionally, after the installation of <br /> the five ground water.wells on the site, all eight ground water monitoring wells were sampled. Each <br /> sample was analyzed for TPH-g, TPH-d and BTEX,with analysis for MTBE, and each sample was <br /> analyzed for the suite of five fuel additives. <br /> Grab Water Samples <br /> TPH- was detected in three of the grab round water samples collected from the site at <br /> • g g g <br /> concentrations ranging from 400,ug/l to 23,000 µg11. TPH-d was detected in all five of the <br /> grab ground water samples analyzed at concentrations ranging from 74 4g/1 to 580,000 gg/l. <br /> • Benzene was detected in two of the water samples analyzed at concentrations ranging from . <br /> 67 4g11 in boring B5 to 370 µg/l in boring B2. Toluene was detected in each of the water <br /> samples analyzed at concentrations ranging from 056µgll in boring B 14 to 57,ug/l in boring <br /> B2. Other BTEX compounds were also detected at concentrations up to 850 µg/1. <br /> ' MTBE was detected in four of the water samples analyzed at concentrations ranging from <br /> 2.1 µg/l in boring B 18 to 2,900 µg11 in boring B2, TBA was detected in three of the water . <br /> samples analyzed at concentrations ranging from 12 µg/1 in boring B 14 to 270 µg/l in boring - <br /> B5. <br /> Analytical results of grab ground water samples analyzed are summarized in Table 4. The laboratory <br /> reports (MAI Laboratory ID 12442 to 12446),quality assurance and quality control (QA/QC) reports <br /> and chain-of-custody forms are included in Appendix D. <br /> Ground Water Monitoring Wells <br /> ' TPH-g was detected in five of the monitoring well samples collected from the site at <br /> Advanced GcoEnvironmental,Inc.. <br />