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' 22 December 1998 <br /> AGE-NC Project No 95-0128 <br /> Page 5 of 8 <br />' 3 3 HYDROCARBON-IMPACTED GRAB GROUND WATER SAMPLES <br /> The results of laboratory analysis of ground water samples collected at the site over the last quarter <br /> are as follows <br /> • TPH-g was not detected in any of the grab water samples collected from the off-site soil <br />' probe borings <br /> • Various BTEX compounds were detected in the grab water samples analyzed from borings <br />' B 13, B 14 and B 17 at concentrations as high as 14 micrograms per liter (µg11) Benzene was <br /> detected only in the sample collected from boring B 13 at a depth of 60 feet bsg, and was <br /> detected at a concentration of 0 61 µg/1 <br />' TPH-d was detected in seven of the eight grab water samples collected at concentrations as <br /> high as 1,200µg/l <br /> • MTBE was detected in seven of the eight grab ground water samples collected from off-site <br /> MTBE was detected at a maximum concentration of 1,400 µg/l in sample B 16-H2O, TBA <br /> was detected In only one sample(B 13-H20B)and was detected at a concentration of 16µg/1 <br /> The Iaboratory reports for the grab water samples (MAT Laboratory ID No MAI Lab No 90585 to <br /> 90592) QA/QC reports and chain-of-custody form are included in Appendix C <br /> 34 HYDROCARBON-IMPACTED GROUND WATER SAMPLES <br /> • During the June 1998 ground water monitoring event, the highest concentrations of <br /> 1 hydrocarbons were detected in the water sample from vapor well VW-1, which contained <br /> 37,000µg/l TPH-g,270µg/l benzene, 1,900µg/1 toluene, 1,600µg/1 ethylbenzene and 7,500 <br /> µg/1 total xylenes TPH-g was detected at a concentration of 29,000 µg/1 from well MW-6 <br />' 0 The highest concentration of benzene detected in ground water samples collected from the <br /> site was from well MW-6 at 870 µg/l <br /> • TPH-d was detected in ground water samples at concentrations as high as 9,200 µg/l (VW- <br /> 1) <br />' 0 MTBE was detected in ground water samples collected from monitoring wells MW-2 <br /> through MW-7 and from vapor well VW-1 Detected concentrations of MTBE ranged from <br /> 2 7µg/l (MW-2)to 1.300 µg/i (MW-5) The approximate lateral extent of dissolved MTBE <br />' is depicted on Figure 4 <br /> Advanced GeoEn,.iron mental Inc <br /> 1 <br />