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• Mr. Gabriel Kars *Project 939-01.09 <br /> April 9, 1992 <br /> Page 2 <br /> The methane concentration was measured next, using a GasTechla model <br /> 1939-OX (GasTech) combustible gas detector. The gas sample was <br /> withdrawn using a motorized pump until the methane reading was <br /> stabilized for a minimum of 30 seconds. The GasTech measures methane <br /> on two scales, 0 to 100 percent by volume and 0 to 5 percent by volume. <br /> Oxygen concentrations are also available, with a measurement range of 0 <br /> to 25 percent by volume. Although not required by the California <br /> Integrated Waste Management and (CIWMB) Title 14 regulations, <br /> oxygen measurements were recorded as a check for potential anomalies <br /> in the methane data. <br /> The GasTech was calibrated at the start of each monitoring day, using two <br /> standard gas mixtures. The high methane scale was calibrated to a gas <br /> mixture of 50 percent methane and 50 percent carbon dioxide. The low <br /> methane scale was calibrated to a gas mixture of 2.5 percent methane in <br /> air. The minimum resolution of the GasTech is 0.05 percent methane by <br /> volume in air. <br /> In conjunction with the gas well monitoring in February, samples were <br /> collected from the intermediate level probes at gas wells GW-1, GW-4, <br /> and GW-10 and analyzed for the ten Calderon Air Solid Waste <br /> Assessment Test (AirSWAT) compounds. The sampling and analysis <br /> protocol used was United States Environmental Protection Agency (EPA) <br /> method TO-14, Determination of Volatile Organic Compounds (VOCs) in <br /> Ambient Air Using SummaO Passivated Canister Sampling and Gas <br /> Chromatographic Analysis. <br /> Before sampling, the gas probe sample zone was purged of one pore <br /> volume of stagnant gas using a diaphragm pump operating at a flow rate <br /> of approximately 1 cubic foot per minute. Each sample was collected <br /> through a Teflon@ tube bypass connection between the pump inlet and a <br /> clean Summa passivated cannister. A fourth Summa cannister was filled <br /> with calibration standard gas and submitted as an analytical blank. The <br /> samples and the blank were sent to a certified laboratory (Air Toxics, Ltd., <br /> Rancho Cordova, California) by overnight parcel service, for gas <br /> chromatography/mass spectrometry analysis of the AirSWAT compounds. <br /> PJ9 9390109.EOW <br />