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Uriah Environmental Services Inc. <br /> U o <br /> o°c oo 2401 East Orangeburg Avenue #675-218, Niodosio, CA 95355 <br /> S00 (510) 455-9991 (209) 551.-3591 (209) 551-1200 <br /> San Francesco-&�V Amn Cen:i n'.'valley FAX <br /> January 22, 1993 RE <br /> Mr. Gerald Sperry V,Q n <br /> Attorney at Law <br /> 1818 Grand Canal Blvd. JAN 1 a 1993 <br /> Stockton, CA 95207 V <br /> RE: Alternative Remediation Technologies Applicable to �� <br /> the Site Located at 2360 East Street, Tracy, CA <br /> Dear Mx. Sperry: <br /> Thank you for the opportunity to review previously acquired <br /> data concerning the above referenced site. Attendant to that <br /> review, Uriah staff are of the opinion that a number of <br /> alternative remediation technologies warrant further study. . . <br /> primary among these are Soil Vapor Extraction-Bioventing, and <br /> Bioremediation. In our experience, both of these technologies <br /> are effective, timely, and typically less expensive than <br /> theexcavation and off-hauling of contaminated soil. <br /> Soil Vapor Extraction and Bioventing Technology Overview <br /> Soil Vapor Extraction (SVE) of organic contaminants in vadose <br /> soils is a process that embraces the principle that many anthro- <br /> pogenic organic hydrocarbons, including those which comprise <br /> gasoline, will volatilize at ambient soil temperatures. Upon <br /> partitioning from the liquid to the gaseous phase, these <br /> contaminants will enter the pore spaces between soil particles <br /> until an equilibrium is achieved. This partitioning is described <br /> by Raoult' s Law. Partitioning into the vapor phase is determined <br /> by the volatility of a contaminant, its solubility in water, <br /> and the degree to which it will adsorb to soil and other <br /> particulate matter. Henry 's Law and vapor pressure are used <br /> to determine appropriate volatility for SVE. Henry' s Law <br /> constants above 0 . 01 (dimensionless) tend to move from aqueous <br /> to gaseous phase. Contaminants with vapor pressures greater <br /> than 25 mm/Hg are generally considered as good candidates for <br /> SVE, with vapor pressures as low as 1 mmfHg acceptable. The <br /> vapor pressure of gasoline is between 37 and 260 mm/Hg depending <br /> upon the degree of weathering (degradation) . <br /> The solubility of gasoline is appropriate to SVE parameters <br /> and, while gasoline may adsorb onto soil and other (organic) <br /> particles within the soil matrix, sorption is generally not <br /> so strong as to preclude efficient SVE remediation. In fact, <br /> 1 . <br />