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' e " 1 I I ' 1 t 1 10 March 2000 r AGE-NC Project No 97-0312 Page 4of6 , � 4 1- ' Calculations for the second area were based on data from boring UST-5 The area was divided into ° four layers, from surface grade to 7 0 meters (23 feet), from 7 0 to 113 meters (23 to 37 feet), from 11 3 to 14 3 meters (37 to 47 feet), and from 14 3 to 15 3 meters (47 to 50 feet) The area of ' impacted soil was arbitrarily defined as 5 meters by 5 meters with all mass calculations based on-this a area For each layer, the maximum concentration detected in soil samples within that layer was assumed for the entire layer ' General site stratigraphy was defined from numerous soil borings advanced at the site Permeability values were estimated from general soil characteristics Climatic parameters were estimated from ' historical local weather conditions An average hydraulic gradient,was based on recent monitoring events fWhen all the Information is entered, SESOIL provides a predicted mass loading to ground water for each year of the test The ATI 23D modeling program used the yearly predicted mass load to ground water from SESOIL and hydraulic properties of the aquifer to estimate the contaminant ' concentrations in ground water at a receptor well To obtain maximum ground water concentrations, the receptor well was placed at the down-gradient edge of the soil contaminant plume The maximum permitted running time of 100 years was used for this site 3.0. FINDINGS Hydrocarbon-impact to ground water was inferred from laboratory analysis and field observations f Ground water elevations were determined by subtracting the measured depths-to-water from the surveyed casing elevations (Table 1) Ground water flow direction was determined by contouring the water elevations on a scaled site plan (Figure 41) I 3 1 - GROUND WATER ELEVATION AND GRADIENT Ground water elevatiori increased an average of 1 34 feet at the former USTs location since the September 1999 morutoring event Ground water flow direction was inferred to be northeasterly at ' a gradient of 0 0009 ft/ft' The flow direction is similar to that inferred for previous monitoring events Figure 4 - Ground Water Elevation depicts the contours for December 1999 Static ground water was approximately 8 feet above the screened interval in UST-2, UST-3 and UST-4, and approximately 5,feet above the screened interval in UST-6 Ground water was within the screened interval of UST-5 " 1 I�r i Advanced GeoEnvaronmental,Inc