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'S <br /> headspace samples were not collected for actual quantification <br /> with relation to soil gas samples so much as to serve a <br /> qualitative function. The data indicate that the ground water in <br /> these wells contains noticeable amounts of dissolved <br /> hydrocarbons. MW1 headspace vapors yielded product odor, and <br /> when an4lyzed, gave a relatively strong response on the <br /> chromatograph. <br /> The soil vapor sampling locations nearest wells 14W1 and MW3, V7, <br /> 1 VB, and V9, elicited only moderate responses. Apparent } <br /> _ <br /> discrepancies_between these soil vapor re�ul��_and monitorin <br /> _ n 9 <br /> .~.T—wel,l.-t-sadspace results-can--be attributed to the very dense soils <br /> encountered at this site. Extremely high vacuums resulted when <br /> the probe assembly was purged, indicating little vapor migration. <br /> The waste oil tank sampling location, V1, also showed moderate <br /> response at shallow depths, most probably due to spillage at the <br /> time of filling. <br /> The major concentration area appears to be on the side of the <br /> pump islands where the product lines couple (Figures 6, 7, and <br /> 8) . Since the two vapor points located directly above the tank <br /> field, V2 and V3, elicited no response, the hydrocarbon vapor <br /> detected at V1 was probably due to the waste oil tank, as opposed <br /> to the tank field. <br /> The SVCA results can be used to estimate a ground-water concen- <br /> tration, using Henry's Law, A Henry's Law constant (H) is the <br /> ratio of a chemical's concentration in air to its concentration <br /> in water at equilibrium. ' It can he estimated by: <br /> H = Csv/Cw (Equation 1) <br /> where <br /> H = Henry's Law constant, atm'L/mole <br /> Csv = vapor concentration, atm <br /> Cw = water concentration, mole/L. <br /> CHV18:B1J 8 <br />