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I ' 07 May 2003 • AGE-NC Project No 95-0143 ' Page 3 of 5 2 2 2 Well Completion I Borings OSW-1 through OSW-17 were completed as ozone sparge wells using 30-mch KVA- ' manufactured ozone sparge points with 0 75-inch PVC blank casing extended to near surface grade The filter pack (No 2116 Lonestar sand) was installed from approximately 25 feet to 21 feet bsg A nominal 2-foot bentonite pellet plug was then installed above the filter pack The wells were then Igrouted to near surface grade with portland neat cement A water-tight,traffic-rated well box was installed over OWS-I through OWS-17 The well locations Iare shown on Figure 2 Ozone sparge well construction is illustrated on Figure 5 ' 3.0. FINDINGS Ground water elevation was calculated and flow direction was inferred from field data, the hydrocarbon impact to ground water was quantified from laboratory analysis I • 3 1 GROUND WATER ELEVATION AND GRADIENT During the December 2002 monitoring event, the average depth to ground water at the site was 17 62 feet bsg Ground water was within the screened intervals of wells MW-10, MW-14 through MW-17 and MW-22 through MW-24, ground water ranged from 1 77 feet to 5 16 feet above the screened interval in the other four monitoring wells The elevation of ground water in the twelve wells was calculated by subtracting the depth to water I from the surveyed casing elevation (Table 1) The average ground water elevation was 8 19 feet below mean sea level(MSL), a decrease of 0 48 feet since the September 2002 monitoring event The inferred ground water flow direction was toward the northeast with a gradient of 0 001 foot/foot IGround water elevation contours for the December 2002 monitoring event are illustrated in Figure 3 3 2 ANALYTICAL RESULTS OF WATER SAMPLES During the December 2002 monitoring event, TPH-g was detected in samples collected from Imonitoring wells MW-3, MW-6 and MW-9 at concentrations ranging from 120 µg/1 (MW-6) to 170,000 µg/1 (MW-3) Various BTEX compounds were detected in the same wells at concentrations as high as 4,600 gg/1 benzene, 51,000 }tg/l toluene,4,500 µg/l ethylbenzene and 27,000 µg/1 xylenes, in sample MW-3 Figure 4 illustrates the approximate extent of TPH-g and benzene contamination • in ground water Advanced GeoEnvironmental,Inc I