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The soil factors which must be evaluated are 1) water content, 2) <br /> porosity, 3) permeability, 4) clay content and 5) adsorption site <br /> density. <br /> The chemical properties of the compound present also needs to be <br /> evaluated. Volatilization is primarily dependant upon the <br /> specific compound's Henry's Law constant which is a measure of <br /> the equilibrium distribution between air and dilute solutions. <br /> In addition, chemical properties such as solubility, concentra- <br /> tion, octanol-water partitioning coefficient and vapor pressure <br /> affect the susceptibility of the chemicals to the in-situ <br /> volatilization process. <br /> In-situ volatilization or in-situ air stripping involves the <br /> removal of volatile organic compounds from subsurface soils by <br /> mechanically drawing or venting air through the soil matrix. A <br /> variation of this process involves the positive pressure flow of <br /> air from a potentially impacted site (e.g. , a building basement) <br /> to divert petroleum hydrocarbon flow. <br /> The unit operations are similar for most in-situ volatilization <br /> systems though the systems vary considerably in size and design <br /> due to site-specific requirements. The basic operations are: <br /> o Injection and/or induced draft fans establish the air flow <br /> through the unsaturated zone. Typically induced draft fans <br /> create a vacuum which draw air through the soils precluding <br /> the use of air injectors. <br /> o Slotted or screened pipe is often used to allow air to flow <br /> through the system but restrict entrainment of soil parti- <br /> cles. <br /> The costs associated with ISV systems vary depending upon the <br /> site characteristics. As described previously, site character- <br /> ization is required prior to system implementation. The estimat- <br /> ed costs associated with the installation and first year opera- <br /> tions of an ISV system are as follows: <br /> Site Characterization $25, 000 <br /> ISV System 25, 000 <br /> Monitoring 10, 000 <br /> Misc. (Manpower, elect, etc. . ) 25, 000 <br /> $85, 000 <br /> Contingency (20%) 17 , 000 <br /> Total Estimate * $102, 000 <br /> * Plus operation and maintenance costs for the <br /> duration of the remediation <br /> 13 <br />