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RULE 4 PERFORMANCE STANDARDS <br />indicated on these maps, the stream channels of Goodspring Creek will be maintained in its natural <br />positions. <br />4.05.5 Sediment Control Measures <br />Sediment control measures to be implemented are shown on the Hydrology - South Map (Map 12) and <br />the Hydrology - North Map (Map 11). These facilities, consisting primarily of diversion ditches and <br />sedimentation ponds, will be located, constructed and maintained to avoid erosion and increased <br />contribution of sediment load to runoff. Discussion on the sediment and drainage control is presented <br />under Section. 2.05.6. The design parameters of the various sedimentation control measures are found in <br />Exhibit 7, Hydrology Information. <br />As necessary, facilities to control sediment will be installed in areas above or below the planned sites of <br />disturbance. "Upstream" facilities, such as temporary diversion ditches and check dams up slope from the <br />mining activities, will divert runoff away from the disturbed areas. Temporary diversion ditches below the <br />disturbed area will divert runoff into sediment ponds. The actual mining areas will aid in retaining <br />sediment within the disturbed areas by catching water in pits, small depressions and dozer basins, etc. in <br />active, unreclaimed mine workings. Water leaving the reclaimed areas will drain into contour furrows or <br />other sediment traps, as necessary, before entering the sedimentation pond. <br />Small Area Exemptions From time to time, it may be necessary to have small areas that do not drain to a <br />sediment pond. Alternative sediment control measures will be used for these areas. These will be <br />designed to meet the requirements of Rule 4.05.2.3 and Rule 4.05.5. Exhibit 7, Item 14-P (Volume 2C) <br />provides a specific design for a small borrow pit needed to construct the embankment for the Section 28 <br />Sediment pond. <br />4.05.6 Sedimentation Ponds <br />The location of all existing and planned sedimentation ponds are presented on the Hydrology - South Map <br />(Map 12) and the Hydrology - North Map (Map 11). The design plans and specifications for the <br />sedimentation ponds are described in this section. The design parameters and detailed sedimentation <br />calculations for the sedimentation ponds are shown in Exhibit 7, Hydrology Information. The <br />sedimentation pond embankment and emergency spillway design are also shown in Exhibit 7, Hydrology <br />Information. All sedimentation ponds will be located as close as practical to the areas to be disturbed. <br />Other methods of sediment control will be located on the reclaimed areas; these methods include the use <br />of contour furrowing, contour drainage ditches, chisel plowing and revegetation etc. <br />This application contains calculations used to determine runoff volumes and flow rates for a theoretical <br />10 -year, 24-hour precipitation event and subsequent sediment volumes. The precipitation data were <br />obtained from the NOA Atlas 2, Volume 3 for Colorado; soil types were obtained from the Soil <br />Conservation Service, and are shown on the Soils - South Map (Map 6) and the Soils - North Map (Map <br />5). <br />The ongoing mining activities within each watershed of the permit area will create constantly changing <br />hydrologic conditions. The design models are generally based on a static, theoretical scenario, utilizing <br />SEDCAD+ which considers a final reclamation and pit closure scenario in each watershed. Refer to Map <br />41 - Watershed Boundaries for Hydrologic Modeling for a delineation of the areas used for these <br />modeling purposes as well as the individual maps associated with each SEDCAD run. The dates indicated <br />on Map 41 are for development of the worst case scenario for hydrologic modeling and are not a <br />definitive schedule for mining and reclamation activities. <br />Rule 4 Performance Standards 4-9 Revision Date: 1/31/18 <br />Revision No.: TR -119 <br />