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• 18 April 1497 AGE-NC-95-0109 Page 2 of 5 collected from each purged well using disposable plastic bailers. Immediately upon retrieval, the samples were transferred into 40-ml EPA-approved VOA vials containing 0.5ml of 18% hydrochloric acid as a preservative and were transported in a chilled container to McCampbell Analytical, Inc. (MAI) under chain-of-custody. This represents the first sampling event for MW-I through MW-5 since ground water fell below the screened interval in 1991 to 1992. All samples were analyzed for total petroleum hydrocarbons quantified as gasoline(TPH-g) and volatile organics j (benzene, toluene, ethylbenzene and xylenes; BTE&X) in accordance with EPA methods 5030/8015m,and 602,respectively. Samples from MW-5,MW-9, MW-12, MW-14 and EW-I were analyzed for methyl tertiary-butyl ether (MTBE). Samples from MW-7, MW-8, MW-9, MW-12, MW-13, MW-14 and EW-I were also analyzed for volatile halocarbons in accordance with EPA method 641. The sample from MW-14 was also analyzed for ethylene dibromide (EDB) in accordance with EPA method 601. Samples were also collected from MW-9 and MW-14 and placed in 40-m1 VOA vials with no added preservative. These two samples were placed in a chilled container and.transported under chain-of- custody to A. Keith Kaufman, M.S., in Culver City, California. These samples were analyzed for physicochemical properties and microbiological enumeration. Table 2 and Table 3 summarize the results of these analyses through March 1997. 3.0. FINDINGS 3.1. GROUND WATER GRADIENT AND DIRECTION The depth to ground water ranged from 53.2 feet below surface grade (bsg) at the north end of the site to 55.3 feet bsg south of the site. The data indicates an average rise of ground water elevation of 2.76 feet since December 1996. Ground water elevations are summarized on Table 1. Ground water elevation contours, based upon data collected on 18 March 1997, are depicted in Figure 3. The flow direction is towards the south and, as in previous monitoring events, the gradient steepens towards the south end of the site. 3.2. MICROBIOLOGICAL ACTIVITY IN GROUND WATER Microbiological plate counts from ground water samples collected during the first quarter of 1997 showed a general increase. Nutrient concentrations have also shown a slight increase at the site during the past quarter. However, absolute numbers of both plate counts and nutrients remain below optimum. Total nitrogen concentrations of 10 parts per million (ppm) to 20 ppm are preferred, and concentrations as high as 100 ppm are acceptable for maximum biodegradation. Chemical and