EXH0281019625

<,-', Table 45. Background Pore-Water Chemistry Assumed for SSL MINTEQ A l'-o _.-,.,- Modeling Efforta Parameter Concentration (rag/L) Aluminum 0.2 Bromine 0,3. Calcium 48 Carbonate 187 Chlorine 15 Iron(+3) 0.2 Magnesium 14 Manganese(+2) 0.04 Nitrate 1 Phosphate 0.0g Potassium 2.gb Sodium 22 Sulfate 25 a Mec_anvaluesfromSTORETdatabaseasreportedinU.S.EPA(1992a). b MedianvaluesfromSTORE-I"database;personalcommunicationfromJ. Allison,AllisonGeosciences. 5.4.3. Assumptions and Limitations. The SSL MINTEQ modeling effort incorporates several basic simplifying assumptions. In addition, the applicabi/it7 and accuracy of the model results are subject to limitations. Some of the more significant assumptions and limitations are described (: • "' below. • The system is assumed to be at equilibrium. This assumption is inherent in geochemical aqueous speciafion rood=Is because the fundamental equations of mass action and mass balance are equilibrium based. Therefore, any possible influence of adsorption (or desorption) zat¢ limits is not considered. This assumption is conservative. Because the model is being used to simulate metal desorption from the solid substrat=, ff equilibrium conditions are not met, the desorpdon reaction will be incomplete and the metal concentration in pore water will be less than predicted by the model. • Redox potential is not considered. The redox potential of the system is not considered due to the difficulty in obtaining reliable field measurements of oxidation reduction potential (Eh), which are needed to determine a realistic frequency distribution of this parameter. Furthermore, the geochemistry of redox-sensitive species is poorly understood. _acdons involving redox species are often biologically mediated and the concentrations of redox species are not as likely to reflect…

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Call to order – Roll Call – Quorum Established – Land Acknowledgement We would like to acknowledge that our Agency operates in four present-day counties, which are the traditional lands of the Coast Salish people, past and present. This acknowledgement does not take the place of authentic relationships with indigenous communities in our jurisdiction and [...]