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2023-01-05_PERMIT FILE - C1981019 (13)
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2023-01-05_PERMIT FILE - C1981019 (13)
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Last modified
9/12/2023 8:24:18 AM
Creation date
9/12/2023 8:15:59 AM
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Template:
DRMS Permit Index
Permit No
C1981019
IBM Index Class Name
Permit File
Doc Date
1/5/2023
Section_Exhibit Name
Rule 4 Performance Standards -ST
Media Type
D
Archive
No
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RULE 4 PERFORMANCE STANDARDS <br /> ,Aqw . 'K"'Lt;R' ., r#er"d-tw.4t-fi-r;.rrw,W +ia4•'.#tra+:<xb{r.,r, r*.rr 'x'✓::n;^.�n,.r,;•.;;, n�.Ks a3n%/,4,K:4ttOn. 4%' <br /> 4.05.5 Sediment Control Measures <br /> Sediment control measures to be implemented are shown in Erosion and Sediment Control Structures(Exhibit <br /> 7 Item 20). These facilities, consisting primarily of diversion ditches and sedimentation ponds, will be <br /> located, constructed and maintained to avoid erosion and increased contribution of sediment load to runoff. <br /> Facilities to control sediment are typically installed in areas above and/or below the planned sites of <br /> disturbance. "Upstream" facilities, such as temporary diversion ditches and check dams upslope from the <br /> mining activities, serve to divert runoff away from the disturbed areas. Because South Taylor mining <br /> activities cover the top of the drainages, no upstream facilities are necessary. Temporary diversion ditches <br /> below the disturbed area will help collect runoff from disturbed areas and route it into the sedimentation <br /> ponds. During active mining, the mining areas will aid in retaining sediment within the disturbed areas by <br /> catching water in pits, small depressions and dozer basins, etc. This captured water and sediment will not <br /> leave the mining areas. Once reclaimed, the basins will drain as they did prior to mining activities (i.e., <br /> historic drainage patterns will be re-established). <br /> All temporary diversions will be removed and reclaimed when no longer needed for sediment control in <br /> accordance with the Operations and Reclamation Plan described in 2.05.4. <br /> Channel lining rock riprap and energy dissipaters will be used when necessary. As stated above, all <br /> temporary diversion structures will be seeded and revegetated. Colowyo does not anticipate that there will be <br /> any significant excess material resulting from the construction of diversion ditches. <br /> None of the diversions will drain into underground mines. <br /> 4.05.6 Sedimentation Ponds <br /> The location, design parameters, and detailed sedimentation calculations of all sedimentation ponds are <br /> presented in Erosion and Sediment Control Structures (Exhibit 7, Item 20). The design plans and <br /> specifications for the sedimentation ponds are described in this section. All sedimentation ponds will be <br /> located as close as practical to the areas to be disturbed. Steep terrain in the upper basins precludes location <br /> of the ponds at the disturbance boundaries, necessitating down-valley locations. Other methods of sediment <br /> control will be located on the reclaimed areas; these methods include the use of contour furrowing, contour <br /> drainage ditches, chisel plowing, and revegetation. <br /> This application contains calculations used to determine runoff volumes and flow rates for the theoretical 10- <br /> year, 25-year, and 100-year, 24-hour precipitation events and 50 percent of the probable maximum <br /> precipitation (PMP), as well as subsequent sediment volumes. PMP information is required for State <br /> Engineer's Office (SEO) requirements for Class II, small to moderate hazard dams. The precipitation data <br /> were obtained from the NOAA Atlas 2, Volume 3 for Colorado; soil types were obtained from the Soil <br /> Conservation Service, and are shown on the Soils—South Taylor(Map 5C). <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 4, which considers the worst-case scenario wherein mine phasing has caused impacts to the entire <br /> disturbance area and reclamation has not yet been attained for any areas. Refer to Map 12 for a delineation of <br /> the areas used for these modeling purposes as well as the individual maps associated with each SEDCAD run. <br /> The dates indicated on Map 12 are for development of the worst-case scenario for hydrologic modeling and <br /> are not a definitive schedule for mining and reclamation activities. <br /> South Taylor/Lower Wilson—Rule 4,Page 4 Revision Date: 12/20/19 <br /> Revision No.: TR-135 <br />
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