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6. POTENTIAL FOR CORROSION AND INCRUSTATION <br />' The potential for corrosion or incrustation of groundwater well casings and screens may be <br /> estimated by considering the following parameters which characterize the inorganic groundwater <br /> quality <br /> • pH <br /> • concentration of dissolved oxygen <br /> • concentration of dissolved hydrogen sulfide <br /> • concentration of dissolved carbon dioxide <br /> • total dissolved solids <br /> • chloride <br /> • carbonate hardness <br /> • iron <br /> • manganese <br /> Potentially corrosive conditions are indicated by low pH, significant concentrations of the <br />' dissolved gases listed above, high total dissolved solids concentration, and high chloride <br /> concentration Potentially incrusting conditions are indicated by high pH, high carbonate <br /> hardness, and significant levels of iron and manganese <br /> The potential for carbonate incrustation, or scaling, can be evaluated by considering the relative <br /> saturation level of calcite Methods for estimating calcite saturation include the graphical <br /> method of Morel and Hering (1993), Langelier's (1936) saturation index, Ryznar's (1944) <br /> stability index, the saturation indices described by Lloyd and Heathcote (1985), and a <br /> thermodynamic approach developed by Snoeyink and Jenkins (1980) A complete <br /> characterization of groundwater geochemistry can be obtained using the software developed by <br /> Allison eta] (199 1) <br />' The Ryznar Stability Index (RSI) was devised to predict the corrosive or incrusting tendencies of <br /> a particular water It is widely used to predict the reaction of solid metals in saturated conditions <br />' A water is corrosive if the index is higher than 7, and incrusting if it is lower than 7 <br /> In order to evaluate corrosion and incrustation potential at the subject site, selected inorganic <br />' parameters will be determined for representative monitoring wells The required analyses are <br /> outlined in Appendix I When these analyses have been performed, the RSI will be calculated <br /> and the potential for corrosion and incrustation will be evaluated <br /> 1 <br /> 1 <br />' WP61 73942 WP1096 TX 5 11 <br />