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13 October 1998 • AGE-NC Project No. 95-0185 ' Page 2 of 4 ' An'alytical, Inc. (MAI). Each sample was analyzed in accordance with the following: • EPA Method 8015m for total petroleum hydrocarbons quantified as gasoline and diesel ' (TPH-g and TPH-d), • EPA Method 8020 for volatile aromatic compounds (benzene, toluene, ethyl-benzene and total xylenes: BTEX) and methyl-tert-butyl ether(MTBE), and • EPA Method 8260m for oxygenated fuel additives di-isopropyl ether (DIPE), ethyl tertiary ' butyl ether(ETBE),methyl-tert-butyl ether(MTBE),tertiary amyl methyl ether(TAME)and tertiary butyl alcohol (TBA). ' 3.0. FINDINGS ' 3.1. GROUND WATER GRADIENT AND FLOW DIRECTION The relative elevation of ground water in each well was calculated by subtracting the ground water '0 depth from the surveyed casing elevation. Monitoring well casing elevations were surveyed relative to MW-4, which was assigned an arbitrary elevation of 60 feet. ' During the June 1998 sampling event, the depth to ground water below the tops of the well casings at the site ranged from 16.35 to 16.83 feet. Ground water elevations have decreased an average 0.64 feet since the last quarterly monitoring event.The ground water flow direction, determined from the data collected during the June 1998 sampling event,was directed toward the southeast,at a hydraulic gradient of 0.005 ft/ft.The relative ground water elevations at the site are contoured on Figure 3. The ' screen interval of all the monitoring wells were appropriate to obtain representative samples of the upper most ground water. ' Ground water at the site has a very low gradient. At such a low gradient, normal measurement error can equal or even surpass the inferred elevation differences between wells, and can greatly influence the calculation of the inferred ground water flow direction. The regional ground water flow direction ' is generally southwest. Small measurement errors or minor changes of local recharge and/or discharge of ground water may have produced the observed variation of ground water flow direction from the regional flow direction. A low gradient generally implies that ground water flow velocity }-is also low at the'site. ' 3.2: LABORATORY RESULTS OF GROUND WATER SAMPLES ' TPH-d was detected in ground water samples collected from monitoring wells MW-1, MW-3 and Advanced GeoEnvironmental,Inc.