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Ms Margaret Lagorio,SJCPHS September 28,2004 Dual Phase Extraction Test Report Joe's Truck Plaza,Lathrop,California Page 6 DPE Test Procedure The DPE test using well MW-7 was conducted for approximately 41 hours and 45 minutes The DPE test was conducted by gradually lowering a 1 5-inch diameter stinger into extraction well MW-7 to approximately 18 feet bgs, total depth of the well is approximately 19 feet bgs The depth to water at well MW-7 prior to the commencement of the test was measured at 8 92 feet bgs Depths to groundwater were also measured in the observation wells prior to the commencement of the test, and the data was used as the baseline to evaluate the drawdown due to DPE The liquid ring pump was used to apply high vacuum to the stinger to extract groundwater and soil vapors from the well Maximum available vacuum from the liquid ring pump was 28 inches mercury (Hg), or approximately 380 inches water column (WC), and the average applied vacuum during the test was 25 8 inches Hg Select wells (MW-1, MW-2, MW-3, and MWQ-1X) were used as observation wells to monitor for changes in groundwater elevation and/or induced vacuums during the test The depth to groundwater and induced vacuum measurements were taken every one-hour during the test period Magnahelic gauges were used to measure induced vacuum Hand- operated electric water-level sounders were used to measure depth-to-groundwater in the observation wells The DPE system was equipped to measure the groundwater extraction rate (discharge from the centrifugal pump after the knockout tank) and soil vapor flow rate (using the pitot tube sensor) Influent soil vapor concentrations were also monitored using a photo-ionization detector (PID) All observations were recorded on field data sheets, which are included in Appendix B In addition, influent soil vapor and groundwater samples were collected and forwarded to a state-certified analytical laboratory for chemical analysis Copies of the certified analytical reports with chain-of- custody documentation are included in Appendix C Laboratory Analytical Methods All groundwater and air samples collected during the feasibility study were forwarded, with appropriate chain-of-custody documentation, to Alpha Analytical, Inc , a California state-certified laboratory (ELAP #2019) located in Sparks, Nevada Groundwater samples were analyzed for TPHG using USEPA Method SW8015B DHS/LUFT Manual, and for benzene, toluene, ethylbenzene, and total xylenes (BTEX), MTBE, ethyl tertiary butyl ether (ETBE), di-isopropyl ether (DIPE), tertiary amyl methyl ether (TAME), and tertiary butyl alcohol (TBA) using USEPA Method SW8260B Vapor samples were analyzed for TPHG using USEPA Method SW801513, and for BTEX and MTBE by USEPA Method S W 8260B 9� P Voe's Truck P1aza\Reports\DPE Test\Joes Truck DPE Test Report doc 5MAW5