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1. H. KLEINFELDER & ASSOCIATES <br /> File: 5-1008-21/12:337 <br /> Revised: July 8, 1986 <br /> Page 6 <br /> gradient well will be placed far enough away from the ° landfill <br /> that it would not pick up any leachate from the landfill if it <br /> were to occur. - <br /> Selection of the casing material w3 t consider the influence <br /> and 'effects the casing material have on the integrity of the <br /> sample and the long-term effect the contaminants may have on the <br /> casing material. Available well casing materials include PVC 21 <br /> (unp2 ticized) , galvanized steel, carbon steel, low-carbon <br /> steel, stainless steel 304, stainless steel 316, and teflon® of <br /> these materials, teflon is considered the best material under all <br /> circumstances except that its cost makes its use as a casing <br /> material impractical. Stainless steel is considered the next <br /> best alternative and its use is recommended at hazardous waste <br /> sites containing high levels of organic contaminants. PVC 1 is <br /> probably the most predominantly used material, primarily for cost <br /> reasons, and is considered an acceptable casing material for <br /> general applications. <br /> In comparing stainless steel to PVC® the following chart <br /> indicates PVC would be more compatible against mineral acid/high <br /> solids, and buffered weak acid conditions: <br /> RELATIVE COMPATIBILITY OF RIGID WELL-CASING MATERIAL <br /> (The values represent x compatibility) <br /> Lo- Stainless Stainless <br /> PVC Galve Carbon Carbon Steel Steel <br /> 1 Steel Steel Steel 304 316 *Teflon <br /> Buffered 100 56 51 59 97 100 100 <br /> Weak Acid <br /> Weak Acid 98 59 43 47 96 100 100 <br /> Mineral Acid/ 100 48 57 60 80 82 100 <br /> Nigh Solids <br /> Aqueous/Organic 64 69 73 73 98 100 100 <br /> Mixtures <br /> Percent Overall 91 58 56 59 93 96 10 <br /> Rating <br /> ' Trademark of Dupont <br /> i�r� 1 <br />