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Tier 1 Spreadsheet <br /> SSTLs are generated one using the "high-end" (or upper estimate) degradation rate <br /> and one using the "low-end" rate defined in the chemical database The values of the <br /> degradation rates in the chemical database may be modified by the user as site-specific <br /> or new information becomes available <br /> For the default parameters in the Tier 1 spreadsheet, modifying the RBSLs using <br /> Green-Ampt produces no noticeable increase in clean-up levels for most chemicals <br /> As the input parameters are changed to reflect site-specific conditions (e g lower <br /> infiltration rate, greater distance to groundwater) the SSTLs calculated with Green- <br /> Ampt may increase <br /> Table H-6 presents the Green-Ampt equations and Table H-7 presents the parameter <br /> definitions <br /> �.3YaD�ON1ENtCQ GR4UND11iiATERiMODEL " ' <br /> In Tier 1, the exposure point in groundwater is assumed to be directly below the <br /> vadose zone source The leaching and groundwater mixing algorithms do not account <br /> for dispersion or degradation in either the vadose or saturated zones The Green- <br /> Ampt model described above is one way to account for degradation in the vadose <br /> zone <br /> The Domenico model is used to account for degradation and dispersion in <br /> groundwater It is applicable for cases where the groundwater receptor point is <br /> downgradient of the source The Domenico equation can be combined with either the <br /> ASTM soil leaching equation (LF,,) or the leaching equation using the Green-Ampt <br /> equations The SSTLs calculated for each of these options are shown on the "SSTLs" <br /> sheet in the Tier 1 spreadsheet. <br /> is <br /> H-5 <br />