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1 13 December 1999 AGE-NC Project No 95-0137 Page 3 of 5 3.0. FINDINGS Ground water elevations and flow direction were calculated from field data and observation and petroleum-hydrocarbon Impact was quantified through laboratory analysis of ground water samples collected during the October 1999 monitoring event 3 1 GROUND WATER GRADIENT AND FLOW DIRECTION ' Depth to ground water at the site ranged from 17 56 to 19 28 feet below the tops of the well casings The data Indicates an average decrease of the relative ground water elevation at the site of 2 75 feet over the last quarter The relative ground water elevation ranged from 79 94 to 81 51 feet The ' relative ground water elevation in each well were calculated from these data The flow direction and the hydraulic gradient were determined by contouring the ground water elevation data on a scaled map of the RFS site (Figure 3) ' The ground water flow direction in the former UST area was generally toward the north and locally � g Y Y northeast However, the gradient is Indeterminant in the area of the former USTs The gradient on the Jimco Truck Stop truck wash area was calculated to be of 0 0075 toward monitoring well MW-7 Historically, ground water flow direction at the site has varied from north to northwest ' The depth to ground water measurements from the vapor extraction wells on the site may not be compatible with those from the monitoring wells, due to limited the screen intervals of the former ' The majority of the data for the ground water contours are from wells with screen intervals that terminate at approximately 30 feet bsg, while the vapor well screens terminate at approximately 20 feet bsg The ground water elevation in well VW-2A is abnormally low for reasons not understood Figure 3 Illustrates the contoured relative ground water elevations as measured on 15 October 1999 ' 3 2 ANALYTICAL RESULTS OF GROUND WATER SAMPLES ' Petroleum hydrocarbons were reported in all wells sampled during the October 1999 monitoring event Benzene was reported in seven of 10 wells sampled at concentrations ranging from 0 68 micrograms per liter (µg/l, MW-3) to 1,300 mg/l (MW-2) Toluene, ethylbenzene and/or xylenes ' were reported in nine of 10 wells sampled at concentrations ranging from 0 50 k4g/l (toluene, VW- 2B) to 1,000 µg/l (xylenes, MW-2) ' TPH-g was reported in samples from each well sampled at concentrations as high as 20,000 Aigll (VW-tA) TPH-d was reported in each well sampled at concentrations up to 18,000 µg/l (MW-3) Advanced GeoEnvironmental,Inc 1