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i ' 04 April 2001 AGE-NC Project No 95-0144 Page 8 of 9 Benzene and toluene were detected in grab ground water samples collected from soli probe boring 15B-12 at concentrations of 8 6 µg/1 and 9 7 gg/l, respectively Ethylbenzene and xylenes were detected at concentrations as high as 3 8 µg/1 and 24 µg/1, respectively, in the grab ground water sample collected from soil probe boring 15B-12 Minor concentrations of ethylbenzene or xylenes were detected in grab ground water samples analyzed from soil probe borings 15B-10 and 15B-13 ' a Fuel additives were not detected above laboratory reporting limits in grab ground water samples collected from the four soil probe borings a The contaminants encountered in the probe soil samples do not appear to be related to the known releases currently under investigation on the site One possible source may be a three- stage clarifier located south of the contamination plume The clarifier was utilized during vehicle washing and steam cleaning activities related to the former repair facility The clarifier is believed to be connected to the city sewer system The location of the three-stage clarifier is illustrated in Figure 2 Figures 4, 5 and 6 illustrate the approximate extent of contamination near the clanfer • Based upon data collected during the ground water monitoring event, AGE concludes Ground water elevation decreased approximately 1 3 feet at the site since the previous ' ground water monitoring event Ground water remained above the screened interval in nine of the shallow wells sampled during the current quarter Ground water elevations in wells completed beneath the clay layer were lower than in wells completed within first ground water • Petroleum hydrocarbons were detected in nine of the ten wells sampled during the November - 2000 monitoring event Average concentrations of TPH-g and TPH-d have remained relatively stable between the August 2000 and November 2000 monitoring events The average concentration of TPH-mo has increased between August 2000 and November 2000 • TPH-g was detected in well sample MW-4, located down gradient of former USTs 3, 4, 5 and 6, and MW 21A and B located within the former UST No 8 pit The plume of ground water impacted by TPH-d is larger than the TPH-g plume, extending at least 40 feet to the southwest of the former UST No 8 pit to MW-19, more than 50 feet ' northeast to MW-20, and more than 100 feet northwest to MW-13 MTBE was detected in ground water samples from MW-13, MW-19A, MW-19B and MW-21 B at concentrations ranging from 1 1 µ.g/1 to 1 6 µg/1 MTBE was not detected in samples from the other seven wells monitored in November 2000 The limited distribution . and low concentrations of MTBE indicate that the impact of MTBE on the site is minimal Advanced GeoEnvironuientai,Inc