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' DRAFT <br />' sequence, the vadose zone contaminant plume is roughly cylindrical in shape, with an <br /> estimated radius of 25 feet, a height of 60 feet, and a volume of 5,000 cubic yards. <br /> t2.5 Hydrocarbon Impacted Groundwater <br /> Based upon the data collected, it appears that the lateral extent of groundwater <br /> contamination has remained relatively constant during the course of the assessment. The <br /> absence of contamination in MW-5 in April and October 1993 (see Table 1) indicates that <br />' there has been a recent decrease in the size of the plume. The plume is roughly circular in <br /> shape with a radius of approximately 50 feet and is centered near MW-1. <br />' 2.5 Aquifer Testing <br /> As reported in the PAR, a slug test was performed on four of the monitoring wells on <br />' November 18, 1993. The hydraulic conductivity and transmissivity of the aquifer were <br /> calculated from data collected during the slug tests. The theory and methods behind the <br /> tests and the results obtained were discussed in section 3.4 of the PAR. The test data (from <br />' the PAR) are included in Appendix A and aquifer calculations are presented in Appendix <br /> B. <br />' 2.7 Vapor Extraction Test <br /> A vapor extraction pilot test was conducted to evaluate the feasibility of vapor extraction <br /> technology for soil remediation at this site. The test was performed using vadose-zone well <br /> RW-1 as the extraction well. The test was conducted on December 17, 1993.The equipment, <br />' methods, and results of the test were described in detail in the PAR. <br /> Three air samples were collected during the vapor extraction test. These samples were <br /> analyzed by a state-certified laboratory for TPH as gasoline and BTE&X. Table 3 <br /> summarizes the laboratory results of the air samples. The results originally appeared as <br /> Table 5 in the PAR. <br />' The results of the vapor extraction test indicated that site conditions are conducive to soil <br /> vapor extraction. <br /> 3.0 SOIL VAPOR EXTRACTION <br />' 3.1 Principles <br />' Vapor extraction is a well known and well-accepted method of in-situ treatment for soil that <br /> has been used successfully at a large number of sites. The method works best on volatile <br /> hydrocarbons in permeable soil. <br /> j <br /> A.&S. 5 <br />