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' Report-Pilot Remedial System Test Page 23 Former Manna Pro Site Project Flo 2013 July 31, 2000 rzero pressure point Based on this chart, the maximum radius of influence of the vapor extraction well VEW-1 is estimated to be 71 feet If the cut-off pressure is set to 1 inch ' of water pressure (rather than 0 inches), then the radius of influence is estimated to be about 55 feet ' The screen-exposed sands had an effective porosity of approximately 0 45 (from the geo- technical laboratory data) This figure may be anomalous due to disturbance of the sample during the sampling process In general, clastic sediments do not exhibit true porosity much in excess of 0 35 Assuming that nearly all of the air recharging into the vapor extraction well was from this sand interval (a reasonable assumption given that it is overlain by relatively pneumatically impermeable silts and clays) and the thickness of this sand exposed above the groundwater surface was about 5 feet, the pore volume for the radius of influence could be calculated ' Effective ROI pore volume =nr2h(p), =3 14(55)25( 45)=21,382 ft ' Given that the amount of air extracted (154,188 cubic feet), the number of pore volumes removed from the area of the radius of influence would be 7 21 Groundwater mounding was observed at the site during the operation of the vapor extraction system Groundwater levels in the wells closest to the vapor extraction well (OB-4 and OB-2) exhibited small but measurable differences in elevation from the initial measurement at 0850 on May 23 to 1000 on May 24 (0 17 feet in OB-2 and 0 13 feet in OB-4) This trend was not repeated during operations from start up on May 30th (0800) ' to the last measurement made on May 31" (0800) before the ICE shut-down The only measurable mounding was from direct measurements made from VEW-1, including measurements made on the last day At the time of shut-down, the depth to groundwater in VEW-1 was 23 20 feet below grade After approximately 20 minutes, the depth to groundwater was measured at 25 65 feet below grade The difference in elevation was approximately 2 45 feet 7.3 Discussion of Air Sparge Field Results Air sparge infection commenced on the second day of the pilot test Air sparging lasted for about 74 hours over 9 calendar days During the sparging, the levels of dissolved oxygen in groundwater were measured in several nearby observation wells The sparging also resulted in a positive pressure observed in OB-3, and consequently this well was tightly capped during sparge operations During sparging, the rate in air infection was generally about 1 scfm (see Summary Table 3 for details) The effect of sparging was also monitored by measuring hydrocarbon levels in the extracted vapor from VEW-1 by the use of an OVM (PID) meter calibrated to a methane standard 2937 Veneman Ave,#B240 Geo-Phase Environmental Inc. Phone(209) 569-0293 Modesto, CA 95356 Fax (209)569-0295 r