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SOP-SG-1 SOIL GAS WELL SAMPLING VVE-T STANDARD OPERATING PROCEDURE LniroarmWSerriceF LInhw1ogy The vapor well samples collected using sorbent tube sampling technique will be conducted as outlined in USEPA Compendium Method TO -17 (Method TO -17). 2.3 LEAK TESTING Before obtaining soil gas samples, leak tests will be conducted. Details of the types of leak tests to be conducted are presented below. 2.3.1 "Shut-in" Test Prior to purging or sampling soil gas, a test will be conducted to check for leaks in the aboveground fittings, i.e., "shut-in" test. The shut-in test will consist of assembling the above ground apparatus (e.g., valves, lines and fittings downstream from the top of the probe), and evacuating the lines to a measured vacuum of approximately 100 -inches of water column, then shutting the vacuum with closed valves on opposite ends of the sampling equipment. The vacuum gauge connected to the line via "T" -fitting will be observed for at least one minute and if there is observable loss of vacuum, the fittings will be adjusted, as needed, until the vacuum in the aboveground portion of the sampling equipment does not dissipate. 2.3.2 Quantitative Leak Testing in the Probe and Sampling Train Following the "shut-in" test, helium will be applied at the connections of the sampling equipment including valves, gauges, tubing, manifold and sample container. Helium will be used for leak tracer testing by placing a shroud over the probe and sampling equipment. Helium will be released into the shroud and a handheld helium detector will be used to monitor and maintain a reasonably steady concentration, which will be recorded on field data forms. The helium concentration in the shroud will be at least 10 -percent or two orders of magnitude higher than the reporting -limit of the field meter used to analyze the sample. Laboratory analysis of the soil gas samples will include testing for helium gas. The analysis of the tracer compound will be used to assess leakage. M