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Report—Remedial Action Feasibility Page 14 <br /> Cutter Lumber—Western Lift Site <br /> GPE Project No 102 3 <br /> August 1,2003 <br /> 6.0 SUMMARY OF SYSTEM PERFORMANCE RESULTS <br /> 6.1 Discussion of Soil Vapor Extraction Field Work <br /> The performance of the vapor extraction system was evaluated by using the system <br /> monitoring data to calculate the total vapor extracted on a weekly basis and using the PID <br /> readings corrected with lab analytic data (see Section 6 1 1) to calculate the total mass of <br /> gasoline hydrocarbons removed on a weekly basis A summary of these calculations is <br /> attached as Summary Table 4 <br />' 6.1.1 PID Calibration with Lab Data <br /> In order to reconcile the PID/OVM reading with less frequent laboratory analysis, it was <br /> necessary to develop an empirical correlation between lab results (measured as mg/L) and <br /> PID readings (measured as ppm) The PID device actually measures ionization potential <br /> of molecules passing through the device, and does not directly measure hydrocarbon <br /> concentration To further complicate matters, the PID is calibrated to a standard gas that <br /> is materially different than the gasoline vapor actually being tested To convert the raw <br /> PID readings from qualitative information to usable quantitative readings, a log-normal <br /> Iscatter plot (Cross-Plot 1) was generated between PID readings and laboratory data for <br /> the points where both types of information were available <br /> The following graph, Cross-Plot 1, depicts the PID calibration data <br /> 1 <br /> I PID Calibration Chart <br /> y = 42 764Ln(x) + 92 544 <br /> 300 <br /> CL <br /> 250 <br /> IL 200 - <br /> 150 <br /> � 100 <br /> a 50 <br /> 1 0 T�A mug <br /> 01 1 10 100 <br /> TPH-G Lab Results (mg/L) <br /> 1 <br /> 2937 Veneman Ave,#8240 Geo-Phase Environmental Inc Phone(209)569-0293 <br /> Modesto,CA 95356 Fax(209)569-0295 <br /> 1 <br />