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System Operation Summary Sod Vapor <br /> Extraction and Emission Control System <br /> 620 West Charter Way StoeMon California <br /> iBased on the vapor sampling analytical results (Table 2), the TPH extraction <br /> concentrations have generally decreased from 14,000 to 200 parts per million by volume <br /> (ppmv) This corresponds to TPH extraction rates of 435 9 and 11 5 lbs/day, respectively <br /> The TPH extraction rates have generally decreased from 435 9 to 11 5 lbs/day The <br /> benzene concentrations have decreased from 1,100 ppmv to less than the laboratory <br /> method detection limit (0 016 ppmv), corresponding to extraction rates of 40 95 and 0 <br /> Ibslday, respectively <br /> HYDROCARBON RECOVERY ESTIMATES <br /> The estimated total mass of TPH extracted, based on FID measurements is 20,920 <br /> pounds; the estimated total extracted mass, based on analytical results is at least 9,045 <br /> pounds The total extracted mass, based on analytical results is extrapolated from results <br /> shown in Table 3 (calculations do not include extraction for the three month period <br /> between 1011192 and 1!7193 when air samples were not submitted for laboratory analysis) <br /> The extracted mass estimate is calculated by averaging two consecutive sampling events <br /> and adding to the previous total The difference in the extracted totals is probably due to <br /> methane in the soil gas which is not detected by the laboratory analysis, but is detected <br /> by the FID The FID measurements have generally been higher than the laboratory <br /> results for vapor samples collected from the influent stream <br />. CONCLUSIONS <br /> Soil vapor extraction has effectively removed an estimated 14,980 pounds of TPH <br /> (average of FID and analytical results-based recovery estimates) from the soil during one <br /> year of operation Significant decreases in BTEX and TPH concentrations and mass <br /> extraction rates from soil vapors have been noted during this period Low concentrations <br /> of volatile organic constituents (other than benzene) continue to be detected (Table 2) in <br /> the influent airstream <br /> Ground water quality under the site has improved considerably based on results of <br /> quarterly ground water sampling conducted between October 1992, and August 1993 <br /> (Table 3) <br /> 91 246J LTR 3 <br />