Laserfiche WebLink
Based on my review and discussions I am confident that the equivalent <br />load posed by the proposed 800 feet high heap will not adversely affect <br />the performance of the composite liner system as well as the liner <br />systems in the PSSAs of the VLF. <br />b. Leachate Pipe System <br />The leachate collection pipe system must remain operational under high <br />heap heights to prevent the development of high fluid heads on the liner <br />system that may increase the amount of leakage through potential liner <br />imperfections. Experience shows that after about 20 percent strain the <br />leachate collection pipes can deform into a "binocular" shape. The analysis <br />presented in Appendix C.3 of the AMEC report indicates that all the pipes <br />will have sufficient capacity under the designed heap heights. It is <br />expected that some of these pipes will be deformed into binocular shapes. <br />Based on my review of leachate pipe system behavior under the <br />equivalent loads posed by the 800 feet high heap there are no concerns <br />related to the pipe capacities under these conditions. There will not be an <br />increased fluid head on the liner system caused by pipe deformation <br />resulting from these high heap heights. <br />c. Heap Leach Material Behavior <br />Pregnant solution is stored in the pore space of the heap at the PSSAs for <br />the different phases. In order to provide adequate storage it is essential <br />that the pore space in the ore does not reduce significantly when it is <br />compressed to the overlying loads. A series of compression and <br />percolation tests are reported in Appendix B.4 of the AMEC report. These <br />tests were carried out to an equivalent height of 565 feet. The percolation <br />through the material was at least ten times that applied in the field and <br />there were very small changes in the overall particle size distribution. <br />Appendix B.3 of the AMEC report provides the results of load-permeability <br />tests on Cresson ore. Figure 7 of this Appendix shows the typical void <br />ratio - log of normal stress plot for the results. Extrapolating this graph <br />indicates that the void ratio (and therefore the porosity, see table below) <br />at an equivalent load of 800 feet will not decrease significantly. <br />The liner puncturing tests described above did not find significant particle <br />break down until the load exceeded an equivalent height of 1,020 feet. <br />The Phase 5 expansion will result in a heap height of about 700 feet <br />above the Phase 4 PSSA, refer to the table above. Based on the <br />compression tests and the liner puncture test results there will not be <br />5