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si 4'iV CLEARw,�JER G R 4 U P, { N C. Irequirements. All data is recorded in a written log by the vapor extraction test technician. Depending on equipment used, some data is also recorded in computer generated printouts or into electronic data logs. DATA EVALUATION Radius of Influence The test is performed at several pressure/flow rate combinations (steps) to" determine the optimal vacuum and flow rate needed to obtain a sufficient radius of influence for one well. The radius of influence will be determined as the radius from the extraction well to a distance from the well where the measured vacuum is one percent of the applied vacuum- (Buscheck &-Peargin, 1991). Alternatively, the I radius of influence may be defined as the estimated distance from the extraction well where vacuums are not less than 0.1 inches of water (Johnson, 1994). This radius of influence is assumed to approximate the maximum distance from the I extraction well at which contaminated soil will be remediated through volatilization. Although there are limitations .inherent .in .determining the radius of influence based on pressure distributions (Johnson & Ettinger, 1994), this method 1Pis generally accepted as a screening technique. The radius of influence may not necessarily increase significantly beyond a certain flow rate.and vacuum. Therefore, the optimal vacuum and flow rate will be based on blower efficiency relative to the ' area of influence and may not necessarily be the maximum vacuum and flow rate. This evaluation will.be determined graphically by plotting the vacuums observed at each monitoring point versus the distance of the monitoring point from the ' extraction well for each step test. Semi-log paper may be used to obtain a straight na line fit through the data for each applied flow rate and vacuum. In addition, the r applied flow rates and corresponding vacuums for each test will be plotted on linear Ipaper to evaluate the effect of vacuum on flow rates. IPermeabili Data collected from several monitoring points during each test will be evaluated to ' determine the permeability of the formation following the method outlined by P.C. Johnson, et al (1990) based on the flow rate and transient pressure distribution data. Two different permeability calculations presented by Johnson, et al (1990) and ' summarized by Dupont (1993) can be performed depending on site parameters. The first calculation assumes radial flow with no vertical leakage and relatively long screens (>,10 ft). The second calculation assumes some vertical flow, shallow soil contamination and relatively short well screens (<10 ft). For a derivation and presentation of the calculations refer to the original references. Soil Vapor Extraction Test Protocols Page 3 of 5 December 1b,1994 I