2016-08-05_PERMIT FILE - C2010089A

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will be constructed before creating new disturbances, unless approved drainage diversions or other surface water control structures are installed. If rills and/or gullies of limited areal extent form which disrupts the approved post mining land use or the reestablishment of the vegetative cover they will be mitigated as soon as practical. Repairs will also be performed in accordance with Rule 4.15.7(5)(a), which means they will be limited to no more than five percent of the acreage initially revegetated during any one year. If a rill or gully feature is identified, New Horizon will utilize appropriate manpower and equipment depending on the ground conditions and the extent of the erosion. This shall include but is not limited to small track dozers, blades, and rubber tired farm tractors. Equipment will be utilized to repair the areas with a minimal footprint as possible. Culverts Design Parameters Culvert designs are presented on Map 2.05.3(4)-1. Culverts were designed using SedCAD software. Subwatershed areas were created for each of the areas flowing to the individual culverts. In general a curve number of 91 was used in the SedCAD program for all of the areas that were disturbed. Three culverts were designed using different curve numbers. Two of the culverts, C -6A and C-613 were designed using a curve number of 79. This use was justified as the watersheds SW -MD and SW-MD2 consist of pasture or rangeland with fair hydrologic conditions and hydrologic soil group C as shown in the SedCAD software and are not a part of the mine disturbance area. The third culvert, C-12, was assigned a curve number of 89 which is compatible with its watershed area, SW2-D, which is a gravel road. Culverts C1 and C13 are also shown in Appendix 2.05.3(4)-7. Ditch Designs The main collection ditches in the permit area are the NHN-001 East and West, the NHN-002 North and South, and the NHN-003 North and South Ditches. These ditches are used to transport runoff into Sedimentation Ponds NHN-001, NHN-002 and NHN-003 for treatment in accordance with the requirements of applicable regulations. The locations of Ponds NHN-001, 002, and 003 can be found on Figure 1 in Appendix 2.05.3(4)-1. All ditches were designed in accordance with the applicable regulations in 4.05.3. Diversions will be designed, constructed, and maintained in a manner which prevents additional contributions of suspended solids to stream flow and to runoff outside the permit area, to the extent possible, using the best technology currently available. Appropriate sediment control measures for these diversions may include, but not be limited to, maintenance of appropriate gradients, channel lining, revegetation, roughness structures, and detention basins. No diversion will be located so as to increase the potential for landslides. When no longer needed, each temporary diversion will be removed and the affected land regraded, topsoiled, and revegetated in accordance with 4.06, 4.14, and 4.15. Diversion design will incorporate the following: Section 2.05.3(4) Page 2 April 2016 (TR -13)