2012-11-05_REVISION - C1982056 (5)

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A brief evaluation of the total projected impact from a 10 -year, 24 -hour rainfall event is illustrative of the effectiveness of chisel plowing and contour furrowing techniques. The projected precipitation from a 10 -year, 24- hour rainfall event is 1.8 inches, or 6,534 cubic feet per acre. The water detention capacity of reclaimed sites prepared with both chisel - plowing and contour furrowing techniques amounts to 5,121 cubic feet per acre, or 78% (1.41 inches) of the projected 10 -year, 24 -hour rainfall event. Therefore, the total amount of water capable of becoming surface runoff from a rainfall event of this magnitude is only .39 inches. Research recently conducted at Energy Mine No. 1 and at the Edna Mine demonstrates that a reasonable estimate for infiltration of water on reclaimed land is 85% of detention capacity (McWhorter 1979; John Gilley, USDA - SEA unpublished data). Hence, the infiltration potential of reclaimed lands within the proposed permit area is 1.19 inches or approximately three times greater than total potential surface water runoff (.39 inches) from a 10 -year, 24 -hour rainfall event. Consequently, the detention capacity and infiltration potential of reclaimed lands taken together, will allow all rainfall to be potentially available for plant growth, and will minimize runoff from reclaimed lands. The aforementioned surface treatments are designed to reduce overland flow of water and shall be supplemented by techniques suggested by Clyde, et al., (1978) if the need arises. The techniques recommended by these researchers include the use of barriers, check dams, erosion stops, matting and roughened surfaces. These treatments can be implemented with various kinds of straw bales, nettings and mattings to effectively reduce overland flow. If results of the annual rill and gully survey indicate excessive erosion has occurred, Twentymile Coal Company will initiate remedial measures. Gullies may be blocked with one of the above - mentioned treatments to provide the opportunity for natural stabilization through the growth of vegetation. Corrective actions, where needed, will be completed by October 31 of the year following the survey. Since the intent of Rule 4.14.6 is to allow stabilization through means other than regrading, every alternative means will be employed prior to using machinery to alleviate an erosion problem. If such action becomes necessary, one of the small rubber -tired farm tractors utilized in reclamation will be allowed on the site to re -grade the gully. Once a site is regraded, it will immediately be planted to the appropriate perennial seed mixture. Details concerning the backfilling and soil stabilization of the Fish Creek Tipple operation are found within Volume VII, Fish Creek Tipple /Loadout Appendix, on pages 2.05 -33 through 2.05 -37. RESPONSE The location and volume of all stockpiled topsoil materials are shown on Map 29, Reclamation. Topsoil stockpiles are located on stable surface areas where the likelihood of disturbance or contamination by the mining operations is minimal. Stabilization of the storage piles has been achieved with one of the perennial seed mixtures. In the event that the side slopes of the revegetated topsoil stockpiles do not become adequately vegetated, then alternate methods may be used for stabilizing the side slopes. The slopes may be reduced to facilitate revegetation or an erosion netting or a geotextile may be placed over areas that are not adequately revegetated. Permit Renewal No. 3 2.05 -107 4/1/99