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• AEGIS ENVIRONMENTAL, INC. STANDARD OPERATING PROCEDURE RE: GROUNDWATER PURGING AND SAMPLING SOP-7 Prior to water sampling, each well is purged by evacuating a minimum of three well-bore volumes of groundwater When required, purging will continue until either the discharge water temperature, conductivity or pH stabilize, a maximum of ten well-bore volumes of groundwater have been recovered or the well is bailed dry When practical, the groundwater sample should be taken when the water level in the well recovers to at least 80 percent of its static level The sampling equipment consists of either a Teflon bailer, PVC bailer, or stainless steel bladder pump with a Teflon bladder If the sampling system is dedicated to the well, then the bailer is usually Teflon, but the bladder pump is PVC with a polypropylene bladder In general and depending on the intended laboratory analysis, 40-milliliter glass, volatile organic analyzer (VOA) vials, with Teflon septa, are used as sample containers The groundwater sample is decanted into each VOA vial in such a manner that there is no meniscus at the top of the vial A cap is quickly secured to the top of the vial The vial is then inverted and gently tapped to see if air bubbles are present If none are present, the vial is labeled and refrigerated for delivery, under strict chain-of-custody, to the analytical laboratory Label information should include a unique sample identification number, lob identification number, date, time, type of analysis requested, and the sampler's name For quality control purposes, a duplicate water sample is collected from each well This sample is put on hold at the laboratory When required, a trip blank is prepared at the laboratory and placed in the transport cooler It is labeled similar to the well samples, remains in the cooler during transport, and is analyzed by the laboratory along with the groundwater samples In addition, a field blank may be prepared in the field when sampling equipment is not dedicated The field blank is prepared after a pump or bailer has been either steam-cleaned or properly washed, prior to use in the next well, and is analyzed along with the other samples The field blank analysis demonstrates the effectiveness of the fn-field cleaning procedures to prevent cross-contamination To minimize the potential for cross-contamination between wells, all well development and water sampling equipment not ATTACHMENT/SCP 7/FEBRUARY 1992