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., ar!Sl .h 'I w "L <br /> — — r 1 <br /> i <br /> t <br /> t <br /> 15 February 2000 <br /> AGE-NC Protect No 98-0448 <br /> Page 14 of 33 <br /> ground water samples are summarized in Tables Nos 1 and 2 <br /> Figures 7 and 8 depict selected soil sample locations and the estimated extent of TPH-g <br /> concentrations adsorbed in soil in cross sectional view,Figure 9 depicts the estimated extent of'TPH- <br /> g concentrations adsorbed in soil in plan view Based on Figures 7, 8 and 9, wells MW-1, MW-2, <br /> MW-4, VW-1, VW-2,'EW-1 and soil borings B-T and B-2 are all located within the adsorbed <br />' petroleum hydrocarbon-impacted soil plume From Figures 7, 8 and 9, a short diameter of 55 feet, <br /> a long diameter of 67 feet and a height of 25 feet were used to estimate a coned elliptical volume of <br /> impacted soil When the data collected at the site is plotted in both pian view and cross sectional <br /> views, the apparent mass of the petroleum hydrocarbon-impacted area yields approximately 613 <br /> gallons of gasoline, the apparent volume of petroleum impacted soil is approximately 893 cubic <br />' yards Mass/volume calculations are included in Appendix I <br /> Figures 5 and 6 depict general hthology beneath the site in cross sectional view, Figure 10 depicts <br /> the estimated extent of dissolved petroleum hydrocarbons to plan,view Based on Figures 5, 6 and <br />' 10, wells MW-1, MW-2, MW-4A, MW-4B, MW-6 and EW-1 are all located within the dissolved <br /> petroleum hydrocarbon ground water plume Based on general lithology descriptions at the site, the <br /> saturated zone appears to be between 20 feet bsg and 50 feet bsg in the area of MW-4, MW-2 and <br /> EW-1 (inner sequence) and between 20 feet bsg and 40 feet bsg in the area of MW-1 and MW-6 <br /> (outer sequence) Therefore, impacted ground water in the inner sequence is assumed to be 30 feet <br />' thick and assumed to be 20 feet thick in the outer sequence, based on the sand content, porosity is <br /> assumed to be 35 percent The distribution of dissolved petroleum hydrocarbons were approximated <br /> by utilizing an equation for two co-centric elliptical sequences, the inner sequence containing the <br /> higher petroleum hydrocarbon concentrations and the outer sequence the lower concentrations From <br /> Figures 6 and 10, the dimensions of the inner elliptical sequence was estimated at a short radius of <br /> 12%2 feet, a long radius of 25 feet and a thickness of 30 feet, the dimensions of the outer elliptical <br />' sequence was estimated at a short radius of 27%2 feet, a long radius of 45 feet and a thickness of 20 <br /> feet An average concentration of 40,000 /..zg/l was used to calculate the mass of petroleum <br /> hydrocarbons remaining in the inner sequence and 5,000 ,ug/l was utilized to calculate the mass of <br />' petroleum hydrocarbons in the outer sequence When the data is calculated, 5 2 gallons of gasoline <br /> -• is dissolved in 229,268 gallons^of ground water at the site Mass/volume calculations are included <br />' in Appendix I <br /> Ground water has been sampled at the site on thirteen occasions During the ground water sampling <br />' events, substantial dissolved petroleum hydrocarbon concentrations have been detected in shallow <br /> groundwater samples collected from MW-1, MW-2, MW-4 and EW-1 Significant concentrations <br /> of dissolved petroleum hydrocarbons have been detected from MW-4B with a screened interval of <br />' 45 to 50 feet bsg <br /> The adsorbed and dissolved petroleum hydrocarboniplume appear to be sufficiently contained within <br /> Advanced GeoFnvi ren mental,Inc <br /> 1 <br /> t <br />