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4.8.1.3 Post Mine Drainages Stabilization <br />Section 4.8.1.3 discusses stabilization of reestablished drainageways on reclaimed range and croplands. <br />A discussion of postmine topography for reestablished drainageways and associated reconstruction crite- <br />ria are in Section 3.5.3. <br />A drainage channel and its tributaries (drainages) are those features which occur on concave segments of <br />slopes, and result in a relatively unbroken, defined channel(s) which can be traced to another <br />down -gradient stream or channel. Any erosional feature which is within twenty-five feet either side of a <br />drainageway will be considered part of reestablished drainageways. A rill or gully outside of the corridors <br />is a sideslope feature and will be handled according to methods discussed in Section 3.6.3.6, Rill and <br />Gully Control Plan. The above definition will aid both Trapper and the Division in distinguishing between <br />those features and areas subject to this section and those subject to Section 3.6.3.6. <br />The final stabilization of drainageways will follow along with vegetative establishment within the drainage. <br />Drainage construction may not be concurrent with initial reclamation of the surrounding watershed. It may <br />be delayed by the overall reclamation process including such things as topsoil haulage safety and future <br />transportation routes, and will be completed when operationally feasible. Where periodic water flow <br />prevents vegetative establishment, a temporary channel may be constructed and maintained until the <br />postmine channel is sufficiently stabilized. When such a method is anticipated, the Division will be <br />furnished design criteria for the temporary channel prior to construction. <br />Once final regrade is complete topsoil will either be laid up to the edge of the drainages (but not within the <br />channel) or the entire drainages will have topsoil replaced. The decision to topsoil or not to topsoil will be <br />based on several criteria. Acceptable erosion control techniques must be feasible such that topsoil in <br />drainageways can be reasonably protected. However, even with protection, runoff events may occur that <br />result in some loss of topsoil from the drainages. Also, superior establishment of vegetation must have <br />been demonstrated through the use of topsoil (see Section 3, 1987-91 Annual Reports). If not, topsoil <br />may not be placed in drainageways. Further, if topsoil placement reduces channel stability, then topsoil <br />will not be placed in drainageways. Where the Division approves rip rap as a channel lining, topsoil will <br />not be placed in the drainageways. <br />Reconstructed drainageways, check dams and deflector dams will be built in accordance with the typical <br />design parameters detailed on Figures 4.8-1a and 4.8-1b. Once the drainageway has reached its final <br />shape and grade through Trapper's reconstruction efforts, application of erosion control practices and <br />materials will be applied where appropriate. <br />It would be impractical to attempt to list every type of product or technique which may be used to stabilize <br />drainageways, particularly since improved products and techniques are constantly being developed. <br />However, the following are possibilities: roving materials, straw bales, brush, erosion control mats, and <br />blankets and soil confinement systems. If Trapper plans to use any of the following, the Division's <br />approval will be obtained prior to use or installation: Drop Structures, Rip Rap Lining or Channel Liners <br />that are impervious. <br />4-183 <br />APR 01 2015 <br />Revision: 10R-0 7 <br />Approved: <br />