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slope erosion, allow the reclaimed banks to blend into the existing natural terrain and allow animals to <br />graze on the sides after final reclamation. <br />Estimates of sediment from the first four refuse areas are included in Illustration 8. The results are <br />listed below. These estimates are based on the entire refuse pile being covered with bare topsoil. <br />The estimates were made using the (USLE) Universal Soil Loss Equation (see Section V.13.4). Since <br />seeding will commence soon after the topsoil is placed, these estimates are conservatively higher <br />than actually anticipated. As vegetation is established, the sediment yield per year will be drastically <br />reduced. When vegetation has been established equal to the premining growth in the area, the <br />sediment yield will be on the order of 25 times less than for bare soil as calculated. <br />Sub -area <br />Top of Pile <br />Face of Pile <br />1 <br />7.1 TPY <br />529.2 TPY <br />2 -3 <br />6.8 TPY <br />1,872.4 TPY <br />4 <br />10.5 TPY <br />1,368.4 TPY <br />The layout of the waste banks and a typical cross section are presented in Maps 76, 77, 77A, and <br />150. The last lift will not be compacted and its top 8 -12" will be scarified to enhance a permeable <br />interface for roots and water. <br />V.13.6 Post Reclamation Sediment Control Sediment Pond DP -1 which collects runoff from the D <br />Portal Area, will be removed during the removal of the Scullion Gulch diversion system when the D <br />Portal Area is reclaimed. A series of three loose rock check dams have been constructed in the <br />Scullion Gulch stream bed and its tributaries in the D Portal Area. The loose rock check dams and <br />other sediment control measures are discussed in Section N.J. The loose rock check dams are <br />shown on Maps 43, 44 and 46. Cross - sections and details are shown on Map 43. The three loose <br />rock check dams will be removed following successful reclamation and revegetation of the D- Portal <br />area upstream. <br />The loose rock check dams will retard streamflow and thereby minimize erosion in the reclaimed <br />Scullion Gulch stream bed. In addition, sediment deposition will occur behind the dams during runoff <br />from small storms. It is anticipated that seepage through the rock dams will be partially blinded off by <br />sediment deposition and thereby provide a minimal amount of settling volume for runoff from small <br />storms. <br />The total storage volume behind the three check dams is 1.74 acre -feet. The 3 year average <br />sediment yield (per USLE) for the reclaimed D Portal Area is 0.51 acre -feet. The three year sediment <br />yield for the total drainage area above and including the D Portal Area is 6.02 acre -feet. Thus, the <br />reclaimed D Portal Area with the proposed contour furrowing and mulching would increase the <br />sediment load in the Scullion Gulch at the D Portal Area by only 9.3% without the check dams being <br />installed. See Illustration 22 for calculations. <br />Midterm Review #6 — MR154 (07/2012) V -14 <br />