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0 0 Clayton Group Services Page 4 Standard Operating Procedures SOP -7 - Groundwater Sampling Grab Mechanisms including bailers and syringe devices that are either reusable or disposable. Bailers are used most commonly and generally are 2 -inch or 4 -inch diameter. Clayton maintains a supply of reusable Teflon®, PVC, stainless-steel, and acrylic bailers and disposable PVC and Teflon® bailers. If a bailer is used, the rope used to raise and lower the bailer should be made of cotton Teflon® and discarded after each sampling. • Suction pumps including centrifugal and peristaltic pumps. These have the disadvantage that they are limited to groundwater at depths of 25 feet or less and may cause the loss of volatiles from the applied suction. • Positive -displacement pumps including gas -drive, gas -operated bladder, electric submersible, and gas -driven piston pumps. Gas -drive pumps may cause gas - stripping of volatile components and for most applications are not recommended. Clayton maintains a 4 -inch submersible pump and a 2 -inch ISCOW Bladder Pump. The attached forms for data collections should be filled in and made a part of the permanent file. All equipment should be decontaminated between sampling episodes in which the same equipment is used and following final use. 7. Filtration - In general, filtration in the field is not done on water samples destined for volatile organic analyses since volatiles may be lost during the filtration process. However, filtration in the field may be appropriate for. water samples where suspended particles may interfere with the analyses such as for dissolved metals and PCBs. The USEPA, in its RCRA Technical Enforcement Guidance Document (1986), recommends that water samples to be collected for metals analyses be collected in two portions, one unfiltered for "total metals" and one filtered through a 0.45 um membrane filter for analyses for "dissolved metals". Field filtration devices fall into three categories: vacuum filtration; pressure filtration; and, in-line filtration generally using glass microfibre or cellulose membrane with a typical pore size of 0.45 um. 8. Sample Preservation - The use of chemical preservation, if any, added to the water sample in the field depends on the analyses to be conducted. Generally, the analytical laboratory will provide sample containers with chemical preservatives that have been added to the containers in the laboratory prior to delivery to the field. The analytical laboratory should be consulted S:AEmir\ProiASOPS\SOP-7.doc