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CONSTRUCTION MATERIALS <br /> Casing and Screen Materials Well casing and screen will be <br />' constructed of clean materials that have the least potential for <br /> affecting the quality of the sample The most suitable material <br /> for a particular installation will depend upon the parameters to <br /> be monitored. Acceptable materials include PVC, stainless steel, <br /> or low carbon steel . <br />' Casing Joints* Joints will be connected by flush threaded <br /> couplers . Organic bonding compounds and solvents will not be <br /> used on points. <br />' Well Screen Slots * Well screen will be factory slotted. The <br /> size of the slots will be selected to allow sufficient <br /> groundwater flow to the well for sampling, minimize the passage <br />' of formation materials into the well , and ensure sufficient <br /> structural Integrity to prevent the collapse of the intake <br /> structure. <br />' Casing Bottom Plug : The bottom of the well casing will be <br /> permanently plugged, either by flush threaded screw-on or <br /> friction cap. Friction caps will be secured with stainless steel <br />' set screws. No organic solvents or cements will be applied. <br /> Filter Pack Material : Filter envelope materials will be durable, <br /> water worn, and washed clean of silt, dirt, and foreign matter. <br /> Sand sire â–ºparticles will be screened silica sand. Particles will <br /> be well rounded and graded to an appropriate size for retention <br /> of aquifer materials . <br /> Bentonite Seal Material Bentonite will be pure and free of <br /> additives that may affect groundwater quality. Bentonite will be <br />' hydrated with clean water <br /> Grout Seal Material , Cement grout will consist of a proper <br /> mixture of Type 1/ 11 Portland cement , hydrated with clean water. <br />' Up to 3% bentonite may be added to the mixture to control <br /> shrinkage. <br /> CONSTRUCTION PROCEDURES <br /> Decontamination : All downhole tools , well casings, casing <br />' fittings, screens, and all other components that are installed in <br /> the well s'^all be thoroughly cleaned immediately before starting <br /> each well installation. When available, each component shall be <br /> I cleaned with a high temperature, high pressure washer for a <br /> minimur of 5 minutes . When a washer is not available, components <br /> shall be cleaned with water and detergent or trisodium phosphate, <br /> rinses' in clean water, then rinsed in distilled water. <br /> Soil and water sampling equipment and material used to construct <br /> the wells shall not donate to, capture, mask, not alter the <br /> I <br />