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R = DuPont Bios jsten. ,r <br /> t,�O i <br /> I <br /> November 2, 1988 Western Regional Office <br /> Job No. 1088-M-4 310 Main Street, Suite F <br /> Pleasanton, California <br /> (415) 462-7772 <br /> San Joaquin County Air Pollution Control District <br /> 1601 East Hazelton Avenue <br /> P.O. Box 2009 <br /> Stockton, California 95201 <br /> Attention: Mr. Likhmir Grewal <br /> Subject: Implementation of Vadose Zone Remediation Plan <br /> Former Econo Gas Station <br /> 43 ' Wash-ington Street <br /> Stockt'-" Calrf-ornia <br /> Dear Mr. Grewal: <br /> The purpose of this letter is to present for your review and <br /> approval an interim plan for vapor extraction of volatile <br /> hydrocarbons in the soil at the Kayo/Fast Gas Station located <br /> at 4325 E. Washington. Street, Stockton, California. A' site <br /> location plan showing buildings and well locations is provided <br /> in Figure 1. <br /> Groundwater levels at this site- have dropped enough to allow <br /> use of existing on-site monitoring wells as vapor extraction <br /> wells. We would like permission to implement an interim <br /> remediation program utilizing soil vapor extraction to address <br /> the contamination in the enlarged vadose zone created by <br /> dropping water levels. Kayo Oil is suggesting this interim ' <br /> plan to take advantage of low water levels to efficiently <br /> remediate this site. <br /> The approved final remediation plan for this site outlines <br /> bioremediation as the primary cleanup process. The interim <br /> remediation plan discussed in this letter, designed to address <br /> contamination in the vadose zone, is to proceed concurrently <br /> with the primary bioremediation plan. <br /> Soil vapor extraction works on the following principles. <br /> Liquid-phase hydrocarbons become adsorbed onto the surface of <br /> soil particles in the vadose zone as a result of surface <br /> tension. Volatile components of the liquid-phase hydrocarbons <br /> vaporize until equilibrium is established in the air space <br /> 368 Turner Way . Aston, Pennsylvania 19014 . 215.497.5800 . 800.548 •1964 POT <br />