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' Report—Fist Phase Remedial System Page 19 <br /> P Y ag <br /> Former Manna Pro Sac <br />' Project No 207 3 <br /> • lune 18, 2002 <br />' regulator and the rotameter and did not enter the sparge wells, but it was found that at <br /> infection rates above 5 to 6 scfm, the oil might not have been completely trapped For <br /> this reason, the sparge rate was never raised to higher levels <br /> From previously documented work, the sands exposed to the vapor extraction well have <br />' an effective porosity of approximately 0 45 (from the geotechnical laboratory data), <br /> although his figure may be somewhat high due to disturbance of the sample material <br /> during the sampling process Assuming that nearly all of the air recharging into the vapor <br /> t extraction well was from the sand interval (a reasonable assumption given that it is <br /> overlain by relatively pneumatically impermeable silts and clays) and the thickness of this <br /> sand exposed above the groundwater surface was about 10 feet, the pore volume for the <br />' radius of influence could be calculated <br /> Effective ROI pore volume = nr2h(p), <br />' 3 14(42)210(45)=24,940 ft' <br /> i <br /> This assumption is based on the previously determined radius of influence of sparging as <br />' 42 feet and the same radius of vapor extraction calculated in this current report Given <br /> that the amount of air extracted (22,000,000 cubic feet), the number of pore volumes <br /> • removed from the area of the radius of influence would be 8$2 Assuming an average <br /> sparge rate of 4 scfm, the total sparge air was about 547,000 scf, and this converts to <br /> about 22 pore volumes Restated, the vapor extraction system moved about 37 times <br /> more air than the sparge system <br /> During the course of operations, one normal quarterly groundwater monitoring event was <br />' completed This was documented in our report of April 23, 2002 The depth-to-water <br /> measurements did not reveal any noticeable groundwater mounding due to the sparging <br /> activities <br /> l <br /> 2937 Veneman Ave, ##8240 Geo-Phase Environmental Inc Phone(209)569-0293 <br /> Modesto,CA 95356 Fax(209)569-0295 <br />