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i <br /> ' 1444 MARIPOSA ROAD <br /> WKA No 2938 06 <br /> • September 6, 2000 <br /> Page 6 <br /> By constructing the risers in this fashion, we essentially created three wells in reverse order <br /> ' Once the excavation was completely backfilled,the wells were plumbed together andlmanifolded <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 Iocated within the former UST excavation are provided in PlatelNo 17 <br /> ' Vapor Extraction Pilot Test <br /> ­ <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 carnes 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(cfrn) <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 an-flow and vacuum in the <br /> vapor extraction well Airflow 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 /> ' The vapor extraction pilot test was conducted for approximately 8 hours A photoiomzation <br /> detector(PID) was used to measure influent hydrocarbon vapor concentrations from vapor <br /> extraction well VEWI PTD readings during the pilot test ranged from 4 parts per million(ppm) <br /> ' to 423 ppm Two vapor-phase activated carbon canisters were used as emission control devices <br /> during the pilot test <br /> • The vapor extraction junction manhole was used as the vapor extraction well and wells'VEW1, <br /> VEW2 and VEW3, MW1, and MW2 were used as the observation wells during the pilot test <br /> o � <br /> WALLACE KUHL <br /> He 7c ed paper Er ASSOCIATES INC <br />