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1444 MARIPOSA ROAD <br /> W ,A No 2938 05 <br /> August 26, 1999 <br /> ' Page 7 <br /> pack of clean pea gravel Because the conductor casing was removed during backfill, none <br /> 1 remained upon completion This design allowed vapors to be removed from the backfilled <br /> material should it be required in the future <br /> B constructing the risers in tins fashion, we essential) created three wells in reverse order <br /> Y g Y <br /> Once the excavation was completely backfilled,the wells were plumbed together and manifolded <br /> so that vapor flow could be controlled to and from individual wells <br /> ' An as-built plan of the existing soil vapor extraction wells VEW1, VEW2, and VEW3 and vapor <br /> extraction framework located within the former UST excavation are provided in Plate No 4 <br /> Vapor Extraction Pilot Test <br /> A vapor extraction pilot test was performed at the site on February 6, 1996 The pilot test was <br /> conducted in accordance with the guidelines and requirements of the SJCPHS and San Joaquin <br /> Valley Unified Air Pollution Control District(SJVUAPCD) Soil vapor extraction is a <br /> remediation technology for removing light end hydrocarbons from the subsurface Soil vapor <br /> extraction works by removing light end hydrocarbons which volatilize and fill the pore space by <br /> inducing air flow through the soil, which then carries the hydrocarbon vapors to soil vapor <br /> extraction wells with subsequent off-gas treatment <br /> The equipment used to perform the test consisted of 1) a 280-cubic-foot-per-minute (cfm) <br /> regenerative blower with a 5 5 horsepower explosion-proof motor; 2) instrumentation for <br /> measuring air flow rate, temperature, vacuum pressure, and volatile organic compound <br /> concentrations, 3) PVC piping, fittings, and wellhead connections, and,4) soil gas sample <br /> collection equipment The vapor extraction unit was used to induce air flow and vacuum in the <br /> vapor extraction well Air flow rate in the vapor extraction well was determined by measuring <br /> the pressure differential across an averaging pitot tube with a magnehelic vacuum gauge <br /> r <br /> The vapor extraction pilot test was conducted for approximately 8 hours A photoionization <br /> detector(PID)was used to measure influent hydrocarbon vapor concentrations from vapor <br /> extraction well VEW 1 PID readings during the pilot test ranged from 4 parts per million(ppm) <br /> `�W <br /> WALLACE KUHL <br /> Recycled paper 6 ASSOCIATES INC <br /> a <br />