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Section No. 6 <br /> . <br /> Revision No 0 <br /> Date September 5, 1991 <br /> Page 15 of 55 <br /> Soil-gas samples will be collected from predetermined locations via <br /> hollow, stainless steel probes The procedure is described below <br /> ■ Probes will be advanced vertically by hydraulic means to the <br /> appropriate sampling depth Placement of probes by this means in <br /> undisturbed soils will provide an air-tight seal Probes will be <br /> designed to allow inlet air to enter only at the required sampling <br /> depth and allow passage of the air to the sample container at the <br /> surface, <br /> ■ Soil-gas samples will be extracted from the subsurface by applying <br /> sub-atmospheric pressure to the probe This pressure gradient will <br /> be established using a teflon-lined diaphragm pump connected to the <br /> sampling probe by flexible tubing, <br /> ■ The sampling apparatus (probe, tubing, and pump) will be completely <br /> purged by evacuating a quantity of gas equivalent to three internal <br /> volumes, <br /> ■ Following complete purging of the sampling apparatus, a soil-gas <br /> sample will be discharged from the teflon-lined diaphragm pump to a <br /> ten-liter Tedlar bag, or directly sampled via a syringe sampler, <br /> o Soil-gas samples contained in Tedlar bags will be handled, <br /> transported and stored in a manner consistent with Section 6 5 <br /> 6.3 5 3 Continuous Air Sampling - Continuous air sampling will be <br /> utilized to monitor air quality for specific health and safety requirements <br /> Continuous monitoring will be performed using portable photo-or flame- <br /> ionization detection equipment with internal pumping systems Sampling and <br /> analysis plan will specify purpose and consideration for such monitoring <br /> 6-15 <br />