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t29 January 2001 AGE-NC Project No. 98-0450 ' Page 3 of 6 ' BTEX and MTBE in accordance with EPA Method 8020. The results of the laboratory analysis are summarized in Table 4. 3.0. FINDINGS ' Ground water elevations were determined b subtracting the measured depths-to-water from the Y g p ' surveyed casing elevations. Ground water flow direction was determined by contouring the water elevations on a scaled site plan (Figure 3). The SVE unit typically operated at an average 145 to 180 cubic feet per minute (cfm) during the period and the IAS unit operated daily. The mass of TPH-g hydrocarbons extracted by the SVE system during the garter was calculated to be approximately 500 gallons. 1 3.1. RELATIVE GROUND WATER ELEVATION AND GRADIENT The depths to ground water from the tops of the monitoring well casings were measured at 46.88 to 47.48 feet. The corresponding ground water elevations ranged from 1.37 to 1.86 feet below mean ' sea level. Over the last quarter, ground water elevation has decreased an average 0.5 feet at the site. The ' ground water elevation data for the well network during the latest ground water monitoring event was depicted in Figure 3. The ground water flow direction determined during this monitoring event was toward the south to southwest, with a hydraulic gradient of 0.005 feet/feet (Figure 3). ' Based on a southerly to southwesterly flow direction within the area contained by the six monitoring wells, wells MW-5 and BMW-2 are down-gradient from the former dispenser system and wells BMW-1 and BMW-2 are down gradient from the former UST area. Table 1 shows.the screen intervals for monitoring wells BMW-3, BMW-4 and BMW-5 and the assumed screen intervals for monitoring wells BMW-1 and BMW-2. The analytical results obtained are believed to be representative of the dissolved hydrocarbon concentrations in the shallow ground water at the site, as the wells are screened across the ground water table. ' 3.2. GROUND WATER SAMPLES ANALYTICAL RESULTS • TPH-g was detected in all samples at concentrations ranging from 73 micrograms per liter (µg/1) in sample BMW-3 to 16,000 µg11 in sample BMW-4. TPH-d concentrations were detected in the Advanced GeoEnvironment2l,Inc.