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3.0 SOIL VAPOR EXTRACTION SYSTEM OPERATION l.. On June 2, 1999, ENSR started the thermal oxidizer soil vapor extraction (SVE) system in the presence of an inspector from the San Joaquin Valley Unified Air Pollution Control District (SJVUAPCD). According to ENSR, five extraction wells (VW-1 D, VW-1 S, VW-2S, VW-3 and VW-4) were utilized by the system, during startup. The system parameters at startup included a flow rate of 214 standard cubic feet per minute (scfm), vacuum of 65 inches of water column, and a concentration AW of volatile organic compounds by Flame Ionization (FID) of 2,100 parts per million by volume (ppmv). During startup, ENSR collected vapor samples for analysis to monitor the efficiency of the SVE system. The system influent soil vapor sample contained 4,960 milligrams per cubic meter(mg/m) �.. of purgeable hydrocarbons, 109 Mg/M3 of benzene, 650 Mg/M3 of toluene, 148 mg/m3 of ethylbenzene, and 560 Mg/M3 of xylenes. This translated to an initial mass recovery rate of 123.5 pounds per day. On June 18, 1999, ENSR monitored the SVE system. The system parameters included a flow rate �,r✓ of 225 to 242 scfm, vacuum of 68 to 73 inches of water column, and a concentration of volatile organic compounds of 600 to 640 ppmv, by FID. Between June 2 and 18, 1999, the system operated for a total of 380 hours with an uptime of 100%. On July 7, 1999, ENSR added catalyst blocks to the system and monitored the system. The �... catalyst blocks cause the system to operate at a lower temperature to reduce natural gas fuel consumption. To maximize recovery rates, the system extracted from VW-2S, VW-3 and VW-4. Between June 19 and July 7, 1999, the system operated for 354.4 hours (78.8% uptime) at an average flow rate of 218 scfm and vacuum range of 87 inches of water column. The system influent soil vapor sample contained 2,160 mg/m3 of purgeable hydrocarbons. On August 18, 1999, ENSR again monitored the system. The system continued to extract from VW-2S, VW-3 and VW-4. Between July 8 and August 18, 1999, the system operated for 925.3 hours (92% uptime) at an average flow rate of 168 scfm and vacuum range of 115 inches of water column. The system influent soil vapor sample contained 1,260 mg/m3 of purgeable hydrocarbons. The total mass removal between startup on June 2, 1999 and the last monitoring on August 18, 1999 is 3,947.32 pounds. 6