2014-07-31_PERMIT FILE - C1981019A

• Permit No: C1981019A
• IBM Index Class Name: Permit File
• Doc Date: 7/31/2014
• Section_Exhibit Name: Rule 4 Performance Standards -ST
• Media Type: D
• Archive: Yes

RULE 4 PERFORMANCE STANDARDS
I' .Ivl -,# 11­41, ;K :•..re'!a x P. - -YW f.,t4,fI e:u#'6+R �.,y{.'%A"s "Yd 'ak�PAB R'. ,: .n4 'wA o-:'.'xmw" ," -,
drainages. The headwaters systems will be restored to historic drainage patterns once temporary diversion
ditches are removed; therefore, there will be no permanent diversions of these channels.
4.05.4 Stream Channel Diversions (Relocation of Streams)
No diversions of perennial streams or streams that drain watersheds that are greater than or equal to one
square mile in size are planned or provided for at this time. The stream channels of Good Spring and Wilson
Creeks will be maintained in their natural positions.
4.05.5 Sediment Control Measures
Sediment control measures to be implemented are shown in Erosion and Sediment Control Structures (Exhibit
7 Item 20). These facilities, consisting primarily of diversion ditches and sedimentation ponds, will be
located, constructed and maintained to avoid erosion and increased contribution of sediment load to runoff.
Facilities to control sediment are typically installed in areas above and /or below the planned sites of
disturbance. "Upstream" facilities, such as temporary diversion ditches and check dams upslope from the
mining activities, serve to divert runoff away from the disturbed areas. Because South Taylor mining
activities cover the top of the drainages, no upstream facilities are proposed. Temporary diversion ditches
below the disturbed area will help collect runoff from disturbed areas and route it into the sedimentation
ponds. During active mining, the mining areas will aid in retaining sediment within the disturbed areas by
catching water in pits, small depressions and dozer basins, etc. This captured water and sediment will not
leave the mining areas. Once reclaimed, the basins will drain as they did prior to mining activities (i.e.,
historic drainage patterns will be re- established).
All temporary diversions will be removed and reclaimed when no longer needed for sediment control in
accordance with the Operations and Reclamation Plan described in 2.05.4.
Channel lining rock riprap and energy dissipaters will be used when necessary. As stated above, all
temporary diversion structures will be seeded and revegetated. Colowyo does not anticipate that there will be
any significant excess material resulting from the construction of diversion ditches.
None of the proposed diversions will drain into underground mines.
4.05.6 Sedimentation Ponds
The location, design parameters, and detailed sedimentation calculations of all planned sedimentation ponds
are presented in Erosion and Sediment Control Structures (Exhibit 7, Item 20). The design plans and
specifications for the sedimentation ponds are described in this section. All sedimentation ponds will be
located as close as practical to the areas to be disturbed. Steep terrain in the upper basins precludes location
of the ponds at the disturbance boundaries, necessitating down - valley locations. Other methods of sediment
control will be located on the reclaimed areas; these methods include the use of contour furrowing, contour
drainage ditches, chisel plowing, and revegetation.
This application contains calculations used to determine runoff volumes and flow rates for the theoretical 10-
year, 25 -year, and 100 -year, 24 -hour precipitation events and 50 percent of the probable maximum
precipitation (PMP), as well as subsequent sediment volumes. PMP information is required for State
Engineer's Office (SEO) requirements for Class II, small to moderate hazard dams. The precipitation data
were obtained from the NOAA Atlas 2, Volume 3 for Colorado; soil types were obtained from the Soil
Conservation Service, and are shown on the Soils — South Taylor (Map 5C).
South Taylor /Lower Wilson — Rule 4, Page 6 Revision Date: 7/21/14
Revision No.: MR -135