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6. Average refuse depth = 130 -feet and a 3% surface slope <br />7. Maximum refuse depth = 350 -feet and a 40% surface slope <br />P P <br />8. Maximum refuse depth = 350 -feet and a 3% surface slope <br />3.1.3 Model Results <br />Percolation through the cover layer and lateral drainage collected in the drainage blanket were <br />calculated for every applicable modeling parameter. The results are shown in following Table 4. <br />3.1.4 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 />control systems. The hydrologic inputs to the modeling, the information used from existing permits <br />and the modeling results are presented below. <br />Hydrologic Inputs <br />Rainfall <br />The SCS Type II, 24 hour precipitation events (NOAA, 1973) and PMP (NOAA, 1984) storm events <br />used in the modeling are listed in Table 5. <br />Soils <br />Soils information was obtained from the National Resource Conservation Service (NRCS) Web Soil <br />Survey (NRCS, 2009). The primary soils within the drainage area for the RPE East are Type D soils. <br />Land Use <br />The following assumptions for land use were used in the SEDCAD modeling based on curve number <br />(CN) recommendations found in NRCS Technical Release 55 (NRCS, 1986): <br />• Undisturbed Slope Areas- CN= 63 for oak -aspen mountain brush mixture in fair condition <br />(30 -70% ground cover) for Type D soils <br />• Reclaimed Refuse Pile- CN =85 for herbaceous mixture of grass, weeds, and brush cover in <br />good condition ( >70 %) for Type D soils <br />PAMpls \06 CO \26 \06261003 MCC Refuse Pile Site Review & Permit \WorkFiles\Permit Application \Text \2010 -04 -19 RPE East Permit Application. docI 1 <br />