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v 08 December 1998 AGE-NC Project No. 95-0109 Page 3 of 5 3.0.. FINDINGS 3.1. GROUND WATER GRADIENT AND DIRECTION The depth to ground water ranged from 51.2 feet below surface grade (bsg) north of the site to 55.1 feet bsg south of the site. The data indicates an average 1.45 feet decrease of ground water elevation since June 1998. Ground water elevations are summarized on Table 2. Ground water elevation contours,based upon data collected on 10 September 1998, are depicted in Figure 3. The inferred ground water flow direction is toward the south. Ground water elevations for MW-1 through MW-5 and vapor wells VW-1 through VW-5 were higher than the surrounding wells. The water measured in these wells appears to be stranded in the unscreened bottoms of the well casings above the surrounding water table. Therefore data from these wells was not used to determine the ground water flow direction. The depths to ground water in MW-6 and MW-9 were higher than expected, based upon data from surrounding wells. Remeasurement of ground water depths following purging of these wells confirmed the ground water depths measured initially. 3.2. MICROBIOLOGICAL ACTIVITY IN GROUND WATER General and selective microbiological plate counts increased dramatically in the ground water sample collected from MW-14 during the third quarter of 1998.Nutrient concentrations also showed an increase in MW-14 relative to the previous monitoring event. Selective microbiological plate counts increased in MW-9 while general plate counts remained relatively stable. Chemical and microbiological data for ground water are summarized on Table 3 and Table 4.The laboratory report (A. Keith Kaufman - 21 September 1998) and chain-of-custody form are included in Appendix B. Concentrations of dissolved oxygen were higher at the time of the June 1998 monitoring event, following addition of hydrogen peroxide to monitoring wells, but had decreased to previous levels at the time of the September 1998 monitoring event. 3.3. PETROLEUM HYDROCARBON-IMPACTED GROUND WATER During the September 1998 monitoring event, petroleum hydrocarbons were detected in ground water samples from five of the seven wells sampled. TPH-g concentrations ranged from below laboratory method detection limits to 4,800 parts per billion(ppb; reported as micrograms per liter). BTEX were detected at concentrations as high as 14 ppb benzene, 21 ppb toluene, 210 ppb ethylbenzene, and 170 ppb xylenes. The highest concentrations were detected in MW-8 and MW-9. The results of analysis by EPA Method 602 for the September 1998 monitoring event are presented Advanced GeoEnvironmcatal,Ine.