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GeofogicafTechnics <br /> .r 1Znc <br /> 2741 River Ryruf <br /> Modesto,Califamia 95351 <br /> (209)538-64241jax#538-5852 <br /> January 26, 1998 <br /> Project No. 251.3 <br /> Project Name: McGranahan(Gawne Road) <br /> Mr. Michael D. McGranahan <br /> Trustee in Bankruptcy <br /> P. O. Box 5018 <br /> Modesto, CA 95352 <br /> Re: Project Status Report <br /> Former Moresco Property, 16865 Gawne Road, Stockton, CA <br /> Dear Mr. McGranahan: <br /> This letter follows our phone conversation of January 22 regarding the remedial action project <br /> for mitigating the gasoline contained in the soil at 16865 Gawne Road, Stockton, CA. <br /> By way of review, the original plan for addressing this site was to perform some type of fate and <br /> transport calculations to estimate the risk of impact the chemicals present at this site would pose <br /> to human health and the environment. These models often lead to the conclusion that either <br /> active remediation or long term groundwater monitoring should be performed. <br /> Generally remediation for a residential site using well water for domestic use is far more actively <br /> pursued than for commercial or industrial areas. Since this is true of this site, and since there was <br /> known gasoline and MTBE present (thought at that time to be higher than we now know them to <br /> have been), it was decided to go straight to remediation, bypassing the fate and transport study. <br /> The goal of the remediation is to remove the contamination and lower the risk. <br /> To this end, a vapor extraction system was installed in early November 1997 and was activated <br /> on November 12, 1997. As the system operated through December we noticed that the <br /> concentration of gasoline vapor in the extracted air started falling off by mid month. <br /> Adjustments were made to the system which brought only temporary increases in vapor <br /> concentration. Vapor extraction efficiency testing showed that the system was operating <br /> correctly. <br /> By the first week in January it became clear that there may not be as much contamination in the <br /> subsurface as originally thought. In light of the vapor extraction results, we decided to review <br /> assumptions used in the mass balance calculations performed in October 1996. Mass balance <br /> calculations are based on the following parameters: <br /> 1. soil density <br /> 2. porosity of the soil <br />