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modeled as a barrier layer. Discharge from the lateral drainage layer (refuse), as calculated by the <br />HELP model, is taken as the seepage rate that infiltration through the pile would discharge to the <br />underdrain. <br />The following eight conditions were used in modeling: <br />Reclaimed Refuse Conditions <br />1. Average refuse depth = 130 -feet and a 40 pecent surface slope <br />2. Average refuse depth = 130 -feet and a 3 percent surface slope <br />3. Maximum refuse depth = 350 -feet and a 40 percent surface slope <br />4. Maximum refuse depth = 350 -feet and a 3 percent surface slope <br />Unreclaimed Refuse Conditions <br />5. Average refuse depth = 130 -feet and a 40 percent surface slope <br />6. Average refuse depth = 130 -feet and a 3 percent surface slope <br />7. Maximum refuse depth = 350 -feet and a 40 percent surface slope <br />8. Maximum refuse depth = 350 -feet and a 3 percent surface slope <br />3.1.3 Model Results <br />Percolation through the cover layer and refuse, and the resulting lateral drainage above the colluvium <br />layer that will be collected by the underdrain, was calculated for the design cases listed above. The <br />model results are shown in Table 4. The model results indicate identical lateral drainage and <br />drainage head values for all eight models. This is interpreted to mean that the initial estimated water <br />content of the refuse and the relatively low permeability of the refuse control the drainage rates <br />predicted by the model. <br />3.2 Hydrologic and Hydraulic Modeling <br />The sediment and clear water diversion ditches and sedimentation ponds were modeled using <br />SEDCAD 4, a computer modeling program that evaluates surface water and erosion and sediment <br />Revised July 21, 2011 IQ <br />26 � tt <br />P \Mpls \06 CO\26 \06261003 RPE E Permit Mod Support \WorkFiles \Permit Apphcation \Text \Exhibit 82 RPEE design 2011 -07 -21 TR 127 doc 14 <br />