2016-08-08_PERMIT FILE - C1981019A (75)

Home Browse Search

RULE 2 PERMITS HYDROLOGICAL BALANCE Postmining Drainage The initial excavation from the mined area was placed in the Streeter Fill, and subsequent excavation is being placed in the area where mining has been completed. Similarly, as mining proceeds into the upper reaches of Streeter Gulch, Gulch A, and Prospects Gulch, overburden material will be backfilled in the mined area adjacent to Gulch A initially, followed by backfilling and reclaiming the areas as mining activities are completed. Later, as the mining proceeds into the area adjacent to a tributary of Taylor Creek, the areas will be progressively mined and backfilled by successively mined overburden and interburden. The final configuration after all mining is completed will be that the entire area will approximate the original topography with some minor variations. These minor variations, which will have no significant affect on the overall hydrology, are the Streeter Gulch mine fill, the West Pit mine fill, a small fill area in Section 16 and the final area in section 16 and adjacent to Taylor Creek, which will be lower than the original ground. Drainage of the mined and backfilled areas will be accomplished by diverting drainage through berm ditches to the reconstructed channels. See Map 19 for channel locations. Berm ditches will be used on all 3:1 reclaimed slopes, including the areas that are not a part of the Streeter Fill. The ditches will be built by cut and fill construction, and will flow towards the permanent mine drainages. The design for berm ditches will be 12 feet wide, slope towards the fill at a minimum of 10%, have a longitudinal grade of 2%, and be located approximately every 100 feet of elevation. These berm ditches are constructed to control the runoff from the reclaimed areas. The replaced topsoil and regraded spoils (especially on 3:1 slopes) are quite susceptible to erosion until vegetation is reestablished. Therefore, the berm ditches will provide protection against excessive topsoil loss during the initial period of revegetation. It is expected that these berm ditches will slowly silt up over a period of years. All premining drainages with defined channels, except some minor drainages, will be restored to approximately their historic drainage condition. Two tributaries to Streeter Gulch, Streeter Gulch and the upper reaches of Gulch A will be reconstructed in approximately their historic location. The upper reaches of Prospects Gulch will be reconstructed in its approximate original location. The reconstructed channel will tie into the existing drainage at the disturbance limit and route water to a sediment pond at the base of Prospects Gulch. The final pit for the East Pit multiple seam operation will be adjacent to an un-named tributary to Goodspring Creek. The upper reaches, above the disturbance limits, of this un- named tributary will be reconstructed slightly south of the original location. This ditch will drain the Final East Pit area to a diversion that routes the drainage to the proposed Prospect Pond. In the proposed West Pit area the tributary to Taylor Creek will be reconstructed along the length of the disturbance. Also in the West Pit area, three additional ditches will be constructed including the West Pit Fill Ditch, the Gulch B Ditch, and the Final West Pit Ditch. other diversion ditches, built on existing natural ground, to collect and route runoff from disturbed areas include the East Side Collection Ditch, the North Prospects Ditch, the South Collection Ditch, Section 16 West Ditch and Section 16 North Ditch. It should be noted that once the West Pit is developed the Section 16 West Ditch, the Section 16 North Ditch, and the Temporary Section 16 Pond will no longer be needed. See Map 19 for the locations of all proposed drainages. The stream channels of Wilson, Taylor and Goodspring Creek will be undisturbed. Although there will be some changes in the areas tributary to the intermittent and ephemeral drainages in the vicinity of the mine, there will be no, change in the major drainage areas tributary to Goodspring Creek, Taylor Creek or Wilson Creek. Premining and postmining tributary areas for the various drainage basins are summarized as follows: Rule 2 Permits 2.04.7-35 Revision Date: 6/23/08 Revision No.: MR-91