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c 0 1: S'I, I; it G 1, t? L t1 G I C Id F: S u N =: , STANDARD OPERATING PROCEDURES RF:GROUNDWATER PURGING AND SAMPLING SOP-4 Prior to water sampling, each well is purged by evacuating a minimum of three well-casing volumes of groundwater or until the discharge water temperature,conductivity,and pH stabilize. The groundwater sample should be taken when the water level in the well recovers to 80%of its static level. The sampling equipment used consists of either a teflon bailer or a stainless steel bladder pump with a teflon bladder. If the sampling system is dedicated to the well,then the bailer is made of teflon, ' but the bladder pump is PVC with a polypropylene bladder. Forty milliliter(ml)glass volatile-organic- analysis(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 a meniscus at the top of the vial. The cap is quickly placed over the top of the vial and securely tightened. The VOA vial is then inverted and tapped to see if air bubbles are present. If none are present,the sample is labeled and refrigerated for delivery under chain-of-custody to the laboratory. Label ' information should include a sample identification number,job identification number,date,time,typo of analysis requested,and the sampler's name, WE®r'l-411 Far quality control purposes,a duplicate water sample is collected tram each well. This sample is put on hold at the laboratory. A trip blank is prepared at the laboratory aLA placed in the transport wcooler. It remains with the coo'.cr and is anal)—d by the laboratory along with the groundwater samples. A field blank is prepared in the field when sampling equipment is not dedicated. Toe field blank is le -cleaned,prior to use in a second well,and is analyzed prepared after a pump or bailer has been steam along with the other samples. The field blank demonstrates the quality of in-field cleaning procedures to prevent cross-contamination. To minimize the potential for cross-contamination between wells,ail the wcll-development and water-sampling equipment that is not dedicated to a well is steam-cleaned between each well. As a r second'precautionary measure, wells will be sampled in order of least to highest concentrations as established by previous analyses. S Rol NEW= 1