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Mr. Wes Johnson Project 16038-700.000 <br /> June 29, 1999 <br /> Page 2 <br /> From Henrys Law: P=H Cw <br /> where: P=equilibrium pressure of chemical in vapor(atmospheres) <br /> H=chemical-specific Henry's Law constant(atmosphere cubic meter/mole) <br /> CW=equilibrium concentration of chemical in water(moles/cubic meter) <br /> and the Ideal Gas Law: P V=n R T <br /> where: V=volume (cubic meters) <br /> n=number of moles <br /> R=Ideal gas constant (0.082 liter atmospheres/mole degrees Kelvin) <br /> T=temperature (degrees Kelvin) <br /> The following relationship is derived by equating the P terms from both equations, <br /> combining n/L (the equilibrium concentration in air in moles per liter) to form Ca, and <br /> solving for Cw: <br /> Cw = RT x Ca <br /> H <br /> The value for RT (24.096 cubic meters atmosphere per mole at 20° Centigrade)becomes <br /> 0.024 when Cw is expressed in micrograms per liter and Ca is expressed in milligrams <br /> per cubic meter. <br /> Groundwater monitoring well MW-5 and soil vapor well CH-2 are adjacent to each <br /> other. Concentrations of VOCs in soil vapor were measured in well CH-2 on <br /> October 1, 1997. These results are summarized in Table 1. The closest date to this event <br /> that groundwater from well MW-5 was tested was September 10, 1997. Review of the <br /> historical chemical results from this well show some variability and thus the results from <br /> September may not represent water quality in October, when the soil vapor testing was <br /> performed. To account for this variability, the groundwater results from one monitoring <br /> event before and after the September event (i.e., June and December) were used. These <br /> results are summarized on Table 1. <br /> EMCOO <br /> SAC:V:\PROJECTS\PJ6\60387000.AS-98\cbell:I Rev.0,06/29/1999 <br /> 16038-700.000 <br />