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significant particle crushing or significant decrease in void ratio under <br />these loads. <br />It is concluded that the heap heights reached above the PSSAs during the <br />Phase 5 expansion will not adversely affect their capacities. <br />3. Dynamic vs. Static Water Balance <br />In previous permit applications the water balance calculations were done using <br />deterministic methods based on monthly intervals. In these models there are no <br />dynamic interactions between various parts of the VLF. For example, it is <br />assumed that on a monthly basis all the leachate that is applied to any part of <br />the heap will report to the PSSA during that month, similarly for precipitation. In <br />the case of very high heaps such as present and future conditions at the Cresson <br />project, this assumption does not hold and recent advances in systems models <br />make it possible to include the dynamic relationships amongst the various <br />components of a system. AMEC used the Goldsim model to develop a dynamic <br />water balance for the Cresson project. <br />Another advance to the water balance model is the inclusion of monthly <br />evaporation values instead of assuming an average of 2 percent evaporation per <br />year. This is an important improvement as it is much more realistic to base the <br />monthly evaporation on site specific conditions. <br />A probabilistic model is used for the monthly precipitation and evaporation and <br />dynamic relationships based on field water balance and flow observations are <br />included. According to Appendix GA of the AMEC report: "The water balance is <br />essentially a "closed" system. All process solutions are contained within the <br />PSSAs of the VLF. Pregnant solutions from the VLF are pumped to the <br />adsorption, desorption and recovery (ADR) plant for processing. The ADR <br />processes the pregnant solutions and returns barren leach solution to the VLF." <br />The outcome is a much more realistic water balance model to analyze the high <br />heap and the complex interactions between the various PSSAs and the ADR. The <br />fluid management system at the Cresson VLF has been improved considerably <br />over the last number of years and this provides higher operational flexibility. <br />The calculated capacities of the PSSAs from the AMEC report are summarized in <br />the following table: <br />PSSA Assumed 80 percent Full capacity <br /> Porosity capacity (MG) <br /> MG <br />I 0.30 34.3 42.9 <br />6