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STANDARD OPERATING PROCEDURES <br /> RE: GROUNDWATER PURGING AND SAMPLING <br /> SOP-4 <br /> Prior to water sampling,each well is purged by evacuating a minimum of three well-casing volumes <br /> of groundwater or. until the discharge water temperature, conductivity, and pH stabilize. The <br /> groundwater sample should be taken when the water level in the well recovers to 80% of its static <br /> level. <br /> The sampling equipment used consists of either a teflon bailer or a stainless steel bladder pump <br /> with a teflon bladder. If the sampling system is dedicated to the well, then the bailer is made of <br /> teflon, but the bladder pump is PVC with a polypropylene bladder. Forty milliliter (ml) glass <br /> volatile-organic-analysis (VOA) vials, with teflon septa, are used as sample containers. <br /> The groundwater sample is decanted into each VOA vial in such a manner that there is a meniscus <br /> at the top of the vial. The cap is quickly placed over the top of the vial and securely tightened. The <br /> VOA vial is then inverted and tapped to see if air bubbles are present. If none are present, the <br /> sample is labeled and refrigerated for delivery under chain-of-custody to the laboratory. Label <br /> information should include a sample identification number,job identification number, date, time, <br /> type of analysis requested, and the sampler's name. " <br /> For quality control purposes, a duplicate water sample is collected from each well. This sample is <br /> put on hold at the laboratory. A trip blank is prepared at the laboratory and placed in the transport <br /> cooler. It remains with the cooler and is analyzed by the laboratory along with the groundwater <br /> samples. A field blank is prepared in the field when sampling equipment is not dedicated. The <br /> field blank is prepared after a pump or bailer has been steam-cleaned,prior to use in a second well, <br /> and is analyzed along with the other samples. The field blank demonstrates the quality of in-field <br /> cleaning procedures to prevent cross-contamination. <br /> To minimize the potential for cross-contamination between wells, all the well-development and <br /> water-sampling equipment that is not dedicated to a well is steam-cleaned between each well. As <br /> a second.precautionary measure, wells will be sampled in order of least to highest concentrations <br /> as established by previous analyses. <br /> I <br />