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1 <br /> 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 /> 1 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. Fraction 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, dart, and foreign matter. <br /> Sand size particles 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 /> ICONSTRUCTION PROCEDURES <br /> Decontamination: All downhole tools, well casings, casing <br /> fittings, screens, and all other components that are installed in <br /> the well shall be thoroughly cleaned immediately before starting <br /> each well installation. When available, each component shall be <br /> cleaned with a high temperature, high pressure washer for a <br /> minimum of15 minutes. When a 'washer as not available,k components <br /> shall be cleaned with water and! detergent or trisodium phosphate, <br /> rinsed in clean water, then rinsed ' an distilled , water., <br /> Soil and water sampling equipment and material used to construct <br /> the wells shall not donate to, capture, mask, nor alter the <br />