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1 <br /> Mr George Takemon Project OF90-002 04 <br /> March 8, 1996 <br /> Page 4 <br /> Percentage Uptime <br /> The system has been operational an average of 78 percent of the time during the fourth <br /> quarter of 1995 (see Table 2) The system was down briefly to repair the sparge blower <br /> The sparge blower also operated an average of 78 percent of the time during the fourth <br /> quarter 1995 <br /> Soil Vapor Concentrations and Flow <br /> The average flow rate through the system has been 170 cfm during the fourth quarter (see <br /> Table 3) Induced vacuums were measured at surrounding monitoring wells to estimate <br /> the radius of influence (ROI) of the extraction system (see Table 4) In the third quarter <br /> 1995, EMCON estimated the ROI to be 60 feet by using induced vacuum data In the <br /> fourth quarter 1995, the ROI is estimated to be approximately 70 feet The ROI has not <br /> changed significantly from the previous quarters <br /> On December 4, 1995, an EMCON technician collected air samples for laboratory <br /> analyses The analytical results indicate that the concentration of TPHG m the soil vapors <br /> decreased from 810 milligrams per cubic meter (mg/m) in the third quarter to 600 mg/M3 <br /> in the fourth quarter Benzene concentrations in the soil vapors decreased from 4 5 mg/m3 <br /> in the third quarter to 0 5 mg/m3 in the fourth quarter (see Table 3) The analytical reports <br /> and chain-of-custody records are presented in Appendix B A total of 570 pounds of <br /> TPHG (or approximately 92 gallons of gasoline) was extracted during the fourth quarter <br /> 1995 (see Table 5) <br /> Destruction Efficiency <br /> During the fourth quarter 1995, the destruction efficiency of the system has been greater <br /> than 90 percent for TPHG (see Table 5) However, the destruction efficiency for benzene <br /> could not be determined as the influent concentration was less than laboratory detection <br /> lunits The emission rate during the fourth quarter was calculated to be less than <br /> 10 pound per day for TPHG (see Table 5) Figure 4 shows the cumulative mass of <br /> petroleum hydrocarbons extracted over time The operation of the remediation system is <br /> in compliance with the requirements set forth by the SJVLIAPCD's Permit-to-Operate <br /> CONCLUSIONS <br /> . Dissolved hydrocarbons detected in groundwater monitoring well MW-14 have decreased <br /> since the third quarter monitoring event Dissolved hydrocarbons were not detected in the <br /> other wells sampled The groundwater flow direction has generally been toward the <br /> SAC1N 1PJ010F9010F900020 4FS-951dms 1 <br />