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i � l <br /> ATC Associates Inc. <br /> 1117 Lone Palm:Avenue, Suite 201 h <br /> Modesto, California 1 <br /> 209-579-222-2221 <br /> fax: 209-579-2225 <br /> Puree Volume Test <br /> To ensure the removal of ambient air from the sampling system and to determine the appropriate <br /> number of purge volumes prior to collecting a representative vapor sample, an initial purge <br /> volume test will be conducted.utilizing one of the temporary soil vapor probe's. One,purge <br /> volume is,estimated-to.be approximately six cubic centimeters per linear%foot of-tubing. The <br /> tubing will be premeasured prior to the installation of the temporary soil vapor probe. A stepped <br /> purge test of one, three, and seven casing volumes will be conducted. The well will be purged at <br /> a rate of approximately 100 milliliters per minute (mL/min) to_200_mL/min. The appropriate <br /> number.of purge.volumes will be selected he an <br /> based_on talyt�-- c d to provided by the onsite_ . <br /> laboratory_associated..with each..stepped purge volume. If.none of the analytes of interest are <br /> detected during the stepped purge test from the selecfed temporary soil gas probe, ATC will <br /> default to-purging three,volumes-prior to sampling each vapor,point. <br /> Leak Test <br /> To ensure leakage of ambient air is not diluting the soil gas sample, a leak test utilizing the vapor <br /> leak check,compound 1,1 difluoroethane -(I-J-DFA), will be conducted at. each-location of <br /> potential ambient air intrusion including sample system connections, surf�ce�bentonite seals, and y <br /> the top of the temporary soil gas probe. The leak check compound will plied during purging <br /> and sampling activities at each soil vapor probe location. The flow rates_ will_be. monitored to <br /> ensure-a sap lin rate of 100 to 200 mL/min. - <br /> _. p g-; r .- <br /> Collection of Vapor Samples <br /> rVI Soilw'vaporsamples will be collected from each of the soil vapor probes using a syringe;provided•1 VR �a d <br /> ;by the analytical laboratory. The ampling equipment will either be dedicated to each soil vapor Ime. ,� <br /> probe or properly decontaminat prior to each use. Prior to ;the collection of vapor samples, the do', <br /> y <br /> appropriate number of purge volumes will be removed from each soil vapor probe as determined ttio%1j""11 <br /> by the stepped purge test. Additionally a leak detector compound will be applied to evaluate if d'a c4- <br /> dilution of ambient air is occurring and to ensure sample integrity. A duplicate sample will be 'b a,nbQ7t <br /> collected from one ofthe soil vapor probes and a trip blank provided by the analytical laboratory <br /> will be included. Vapor sample will be.collected in-accordance with the DISC..-guidelines <br /> entitled;Advisory-Active Soil Gas Investigations dated January 28, 2003 and 'Interim Final e <br /> Guidance for the Evaluation and Mitigation of Subsurface Vapor Intrusion to Indoor Air dated <br /> December 15, 2004,revised February 7,2005. <br /> Sample Analysis t t <br /> Soil vapor samples collected from the soil vapor probes will be immediately transferred under <br /> chain-of-custody procedures to an onsite State-certified laboratory. The samples will be analyzed <br /> for total petroleum hydrocarbons as gasoline (TPHg); benzene, toluene, ethylbenzene, and <br /> xylenes (BTEX), methyl tertiary butyl ether (MTBE), tertiary butyl alcohol (TBA), di-isopropyl <br /> S\Environmental\62605Udeports2007 November.doc 4 <br />