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undisturbed virgin ground at the top of a final highwall where the final slopes may exceed 3H: IV. As <br />indicated in Tab 20 of the permit, slopes could exceed 3(h):1(v) in isolated areas above the final <br />highwall where the natural slope was originally steeper than 3(h):1(v). A sensitivity analysis was run to <br />determine the factor of safety for the backfill by varying the input factors for saturation, pit slope heights <br />and final surface slopes. The stability report and data are included in Attachment 20A. Based on the <br />results of the stability report all slopes were designed to achieve a static factor of safety of at least 1.3. <br />Included in the postmine regrading operation was the construction of small swales and hummocks to <br />minimize erosion and to conserve soil moisture and to promote revegetation. These features were <br />constructed on steeper slopes in the reclaimed area. <br />SCC generated topographic maps, using photogrammetric methods, of backfilled and regraded areas on <br />an annual basis. These maps were submitted to the Division each year in the Annual Reclamation <br />Report. The maps were used to determine whether regraded areas were consistent with the approved <br />postmining topography. <br />Each year Seneca also submits a Rill and Gully Survey. This annual report is produced by inventorying <br />erosional features on the hillslopes and drainage channels where additional repairs and maintenance <br />work are identified. The 2009 survey map was referred to during the bond release inspection. <br />Drainage reconstruction <br />The approved drainage reestablishment consisted of the design and construction of permanent <br />postmining drainage channels in the original permit area. The Postmine channels are shown on <br />Figure 2. of this document. Postmine channels are designed and certified to safely convey the peak <br />discharge from the 10-year, 24-hour storm event in accordance with Rule 4.05.3 and do not require as- <br />built certifications. Certified designs for the post-mine channels were approved prior to the bond release <br />application and are provided in Tab 20 Attachment 20-1 of the permit. The approved Post-Mining <br />Topography Map, Exhibit 20-2 shows the location of the approved post-mine channels. Exhibit B of <br />the SL-2 application, "Postmine topography and Drainage" shows the completed drainage channels. <br />In the original permit area Postmine Channel 005 Gulch, and its' tributary 005-E1, flow to Pond 005 <br />which discharges through an unnamed drainage into Dry Creek. Postmine Channel 006 Gulch, and <br />its' tributaries: 006-NE1, 006-NE2, 006-NE3, 006-E1, and 006-E2 flow to Pond 006 which <br />discharges into Hubberson Gulch which also flows into Dry Creek. Several other designed <br />permanent tributary drainages were approved through revisions to the permit, including 005-W1, <br />006-S1, 006-NE3, and 006-NE4. Additional tributary drainage channels have been "field fit" in <br />accordance with provisions of the approved rill and gully repair plan, in locations where concentrated <br />flows on the reclaimed landscape resulted in channel formation. <br />Facilities <br />The final reclamation plan for the Seneca II-W Mine includes retention of numerous permanent facilities <br />in the original permit area including access and light use roads, an electric substation and powerline, <br />and various fences associated with grazing management, property boundaries, and shrub plots.