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Exhibit E <br />exceeding existing conditions and providing adequate protection until vegetation is established. <br />• Because the reclaimed mining surface will be lower than natural topography at the highwalls, additional <br />channel protection measures are required. These measures include a rock-lined, sloping drop structure, <br />which can convey the 100-year flood down the steeper slopes (4h:Iv). The drop structure, limited to a <br />drop height of 10 feet, can be formed into exposed rock or created using mined rock. The structure is "V- <br />shaped" to concentrate flows in the center and includes a scour basin, energy dissipater, which transitions <br />the flow to the reconstructed arroyo. This approach will allow existing arroyos to be transitioned into the <br />reconstructed drainage at the upper end of the mined area. <br />When establishing the final reclamation surface, consideration was given to the existing arroyo watershed <br />boundaries. The final reclamation surface includes a small "ridge" to allow surface runoff to flow towards <br />the restored arroyos, resulting in approximately the same watershed area. This approach will provide <br />reasonable assurances that peak flows and runoff volumes will not be increase over existing conditions. In <br />addition, since the final reclamation surface is flatter than existing topography, runoff peaks and sediment <br />loads will likely be less than existing conditions. <br />Additional watershed reconstruction information is provided in Exhibit D - Mining Plan and Appendix F <br />"Surface Water Management Plan." <br />TOPSOIL & SUBSOIL RECONSTRUCTION <br />Topsoil and subsoil reconstruction activities will be scheduled to allow completion of soil amendment, <br />surface manipulation activities and revegetation activities when ground conditions are favorable to <br />minimize adverse impacts to soil resources and during the appropriate season to optimize seedling <br />• establishment. Topsoil and subsoil replacement operations may be conducted with a variety of suitable <br />equipment (i.e., scraper, truck/shovel, truck/loader, backhoe, dozer, etc.). Mobile equipment will be used <br />to replace topsoil and subsoil materials that will be either direct-hauled from on-going salvage operations <br />or removed from topsoil stockpiles. Mined out areas will be reclaimed by placing the overburden material <br />from the adjacent panel on the floor of the pit and reapplying the subsoil and topsoil. . <br />Suitable topsoil and subsoil available for replacement over the leveled backfill will result in an average <br />replacement depth of six inches of topsoil and 12 inches of subsoil. Varying topsoil depth and quality in <br />association with topographic features will help minimize erosion and deposition processes, optimize soil <br />resource productivity and aid in development of vegetation communities. Topsoil and subsoil thickness <br />may be increased on stable land forms (i.e., flatter areas) to foster increased vegetation productivity. <br />Decreased topsoil and subsoil depths may be constructed on slopes and other landforms where soil <br />erosion potentials are higher. Preferably, soil reconstruction materials with higher rock content would be <br />placed on steeper slopes to protect them against excessive erosion and promote the growth of woody <br />species. Different topsoil/subsoil depths associated with topographic position will encourage plant species <br />diversity based upon changes in slope, aspect and available soil moisture. <br />Direct Haul Topsoil Placement. Rio Grande plans to direct-haul salvaged topsoil and subsoil materials <br />to final graded and ripped backfill whenever possible. Direct-haulage of topsoil and subsoil will optimize <br />the transfer of nutrients, organic matter, microbial populations, and residual native seed bank. When <br />direct-haulage of topsoil and subsoil is performed outside of the active growing season, increased <br />volunteer growth of plant propagules is supported. The following topsoil/subsoil replacement plan will be <br />utilized when the salvaged soil is being directly hauled and placed on final graded backfill: <br />• • Suitable subsoil (AC and/or B-horizons) will be directly hauled and placed to an average 12-inch <br />1180-Mine Permit Exhibits (Jul.05.02)FINAL.doe E-3 <br />July 8, 2002