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a w a9 \Ys:sr :: ict\ (; tiut.uc; tt: Iti;suuttc:IiS llfNI. JLA STANDARD OPERATING PROCEDURES 41, RE.GROUNDWATER PURGING AND SAMPLING amiiv SOP-4 Prior to water sampling, eech 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%n 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 it dedicated to thr well,then the bailer is made of teflon, E` but the bladder pump is PVC with a polypropylene bladder. Forty milliliter(ml)glass volatile-organic- analysis(VOA)vias,with teflon septa,are usi:tl as sample containers. The groundwater sample is decanted into each VOA vial in such a mane: that there is a ' meniscus at the to of the vial. The ca is quickly laced over the la of the vial and securely tightened. P P 9 Yp p � ` The VOA vial is then inverted and lapped to see if air bubbles are present. If none are present,the r sample is labeled and refrigerated for delivery under chain-of custody to the laboratory. Ubcl information should include a sample identification number,job identification number,dale,time,type of analysis requested,and the sampler's name. W' .�Vs_ For quality control purposes,a duplicate water sample is collected from each well. This sample is put on hold at the laboratory. A trip blank is prepared at the laboratory and placed in the transport cooler. It remains with the cooler and is analysed by the laboratory along with the groundwater samples. A field blank is prepared in the field when sampling equipment is not a Acated. The field l blank is prepared after a pump or bailer has been steam-cleaned,prior to use in a second well,and is O =` analyzed along with the other samples. The field blank demorstrates the qu&lity of in-field cleaning procedures to prevent cross-contamination. To minimize the potential for ci oss-contamination between wells.all the well-development and ® water-sampling equipment that is not dedicated to a well is steam-cleaned between each well. As a second precautionary measure, wells will.be sampled in order of least to highest concentrations as established by previous analyses. i 1